Syn hesis and Cha ac e iza ion o Homogeneous and
Su ace A ached Ca alys s o Small Molecule
Ac i a ion
Disse a ion submi ed o he
Facul y o Ma hema ics and Na u al Sciences
Ins i u e o Ino ganic Chemis y
Ch is ian-Alb ech s-Uni e si y
o Kiel
o he deg ee o
D . e . na .
Submi ed by
S en F oi zheim
Kiel, 2024
1. Gu ach e : P o . D . F. Tuczek
2. Gu ach e : P o . D . C. Nä he
Tag de mündlichen P ü ung: 08.11.2024
Zum D uck genehmig : 08.11.2024
De Dekan; P o . D . F ank Kempken
I
This Thesis was w i en a he Ins i u e o Ino ganic Chemis y
o he Ch is ian-Alb ech s-Uni e si y o Kiel
unde he supe ision o P o . D . Felix Tuczek
be ween Ma ch 2018 and Oc obe 2023.
III

Acknowledgemen
Als e s es möch e ich mich bei meinem Dok o a e P o . D . Felix Tuczek ü die Möglichkei
meine Dok o a bei in seinem A bei sk eis anzu e igen bedanken. Neben den spannenden und
ielsei igen Themen in de Fo schung, gelang es uns ein paa seh hochwe ige und leh eiche
Vo lesungen in den d ei Co onasemes e n zu ges al en.
He n P o . D . Ch is ian Nä he danke ich ü die Übe nahme des Zwei gu ach ens, dem
Lösen de Eink is alls uk u en und die Mi a bei an den Publika ionen.
Ein besonde e Dank geh auch an D . Tobias Engesse . Danke ü die ielen S unden de
Diskussion übe Spek en, Rechnungen und un e s andene E gebnisse, die Un e s ü zung bei
de zwei en Publika ion, das Ko ek u lesen de A bei und wenn es nö ig wa - das S ubsen
in die ich ige Rich ung.
D . Jan K ahme danke ich ü die ielen und eilweise seh langen NMR-Messungen. Auch
danke ich di ü die S a hil e bei de Elek ochemie. Das En enzeichnen ha Spaß gemach .
Nicolas Le Poul danke ich ü die olle Koope a ion, den Wissensaus ausch und die in ensi e
Be euung wäh end unse es Au en hal s in B es . Danke auch ü die Au nahme jenen Fo os,
welches die Basis ü das F on co e unse e Publika ion bilde .
Mein Dank geh auch an S ephanie Pehlke und Jaqueline Pick ü die Au nahme de Elemen a -
und Halogenidanalysen.
Dem A bei sk eis Tuczek danke ich ü die olle Zusammena bei und S immung wäh end
meine Zei . Die Au en hal e in Sehlendo gehö en dabei de ini i zu meinen Highligh s.
Ein besonde e Dank geh auch an die S icks o ixie ung und o allem an Jannik Junge.
Danke ü 5 Jah e mi iel Spaß, we ollem wissenscha lichen Aus ausch und eine ollen
Zusammena bei - ohne dich hä e es nu halb so iel Spaß gemach .
Ein g oße Dank geh auch an meine Kommoli onen und F eunde, die mich übe die ielen
Jah e beglei e haben. Ch is oph Bohl, Daniel Hugenbusch, Ma c Leh , Jonas an Din e ,
Jannik Junge, Jannik Benecke, Tobias Haase, Felix Ha mann, Kai Uwe Clausen und Timo
Rabe - ih seid die bes en und hab meine Zei in Kiel zu e was ganz besonde em gemach .
Zu gu e le z möch e ich mich noch bei meine Familie bedanken. Besonde s bei meine
Mu e und Rol . Ohne eu e iesige und bedingungslose Un e s ü zung wä e ich nie sowei
gekommen. Abschließend möch e ich mich noch bei meine Ve lob en Sina bedanken. Danke
ü den Rückhal und den gemeinsamen All ag. Ich eue mich au unse e gemeinsame
Zukun !
IV
Lis o Publica ions
This hesis consis s o h ee pa s. Two o hem a e based on he ollowing publica ions, which
a e published in di e en jou nals:
1.
J. Junge, S. F oi zheim, T. A. Engesse , J. K ahme , C. Nä he , N. Le Poul and F. Tuczek
"Tungs en and Molybdenum Dini ogen Complex Suppo ed by a Pen aden a e Te apo-
dal Phosphine Ligand: Compa a i e Spec oscopic, Elec ochemical and Reac i i y
S udies"
Dal on T ans., 2022, 51, 6166-6176. DOI: 10.1039/D1DT04212B
2.
S. F oi zheim, J. Junge, C. Ba nehl, T. A. Engesse , J. K ahme , C. Nä he and F. Tuczek
"Molybdenum ica bonyl complexes suppo ed by linea PNP ligands: In luence o P-
and N-subs i uen s on ela i e s abili y, s e eoisome ism and on he ac i a ion o small
molecules"
Eu . J. Ino g. Chem. 2023, 26, e202300280. DOI: 10.1002/ejic.202300280
V
Ku zzusammen assung
Die syn he ische S icks o ixie ung be ass sich mi de Bindung und De i a isie ung des
sons ine en Dis icks o moleküls mi hil e on Übe gangsme allkomplexen. Im Fokus de
Be ach ungen s ehen hie bei o allem Molybdän und Wol am, die häu ig mul iden a e
Liganden binden. Diese A bei is d ei in Abschni e un e eil . Im e s en Abschni is die
Syn hese und Cha ake isie ung des [W(N
2
)(P
Me2
PP
Ph2
)] Komplexes besch ieben, welche
au dem on de A bei sg uppe Tuczek en wickel en pen aPod-Ligandsys em basie . Auch
wenn diese Komplex eine ge inge e ka aly ische Ak i i ä (mi SmI
2
/H
2
O) als sein molyb-
dänbasie es Analogon hinsich lich de E zeugung on Ammoniak zeig e, is diese Komplex
das e s e Beispiel ü einen wol ambasie en Dis icks o komplexes, de übe s öchiome ische
Mengen NH
3
gene ie en konn e. Ein Ve gleich de Eink is alls uk u en de Mo- & W(N
2
)
Komplexe zeig nu ge inge s uk u elle Un e schiede. Um Hinweise au die U sache ü die
un e schiedliche ka aly ische Ak i i ä zu inden, wu den elek ochemische und spek oelek-
ochemische Un e suchungen du chge üh . Es wu de ge unden, dass die Komplexe g oße
Un e schiede hinsich lich ih e S abili ä im oxidie en Zus and au weisen.
Im zwei en Teil diese A bei wi d, s a N
2
, CO als Ligand e wende . Kohlens o monoxid
is isoelek onisch zu Dis icks o , bilde jedoch s abile e Komplexe, was die Un e suchung des
Koo dina ions e hal ens on Ligandensys emen e möglich . Es wu de das Koo dina ions e -
hal en on iden a en PN
Ph
P
R
Liganden (R = Ph
2
, E
2
, Cyp
2
,
i
P
2
, Cy
2
) an das Mo(CO)
3
S uk u agmen un e such . Es wu de ge unden, dass alle Liganden in eine acialen Ge-
ome ie koo dinie en, obwohl DFT-Rechnungen zeigen, dass eine me idionale Geome ie
ü s e isch ansp uchs olle Res e be o zug wä e. Diese E gebnisse s ehen im Gegensa z zu
den in de Li e a u bekann en [Mo(CO)
3
PN
H
P] Komplexen, die ü Phosphindono en mi
s e isch ansp uchs ollen Subs i uen en auch eine me idionale Geome ie zeigen. DFT-S udien
mi [Mo(CO)
2
PN
R
P
Me
] (R = N, Ph) zeig en un e ande em, dass de Übe gangzus and
des PN
Ph
P
Me
hal igen Komplexes ene ge isch höhe lieg , was au die Bildung agos ische
Wasse s o b ückenbindungen zu ückzu üh en is .
Im d i en Teil diese A bei wu den iden a e Ligandsys eme ü eine mögliche Fixie ung
au eine Goldobe läche un e such . Hie zu wu den e schiedene Ansä ze gewähl , wobei de
Haup okus au de Syn hese eines [Mo(CO)
3
PN
Ph
P
Ph
] Komplexes lag, de in pa a-Posi ion
zum N-Dono mi eine Thio-G uppe e sehen wa , die als Anke g uppe au de Obe läche
dienen soll e. Als g öß e He aus o de ung s elle sich hie bei die Ein üh ung de gewähl en
SCN-G uppe he aus, da im Zuge diese Reak ion B
2
eigese z wi d, welches die Phosphine
oxidie e. Die Schü zung de Phosphine mi Bo ang uppen e laub e schlussendlich die Ein-
üh ung de SCN-G uppe. Leide konn e de gewünsch e Ligand dennoch nich e hal en
we den, da Saue s o e un einigungen im Mo pholin bei de En e nung de Bo ang uppen
die Phosphine oxidie en. Nich sdes o o z s ell die o ges elle Rou e eine iel e sp echende
Me hode zu Da s ellung des PN
Ph-SCN
P
Ph
Liganden da , welche im Anschluss ü die
Koo dina ion an [Mo(CO)3(ch )] e wende we den könn e.
VI
Abs ac
Syn he ic ni ogen ixa ion deals wi h he binding and de i a iza ion o he o he wise ine
dini ogen molecule wi h ansi ion me al complexes. These complexes p ima ily con ain
molybdenum and ungs en cen e s, which mos ly bind mul iden a e ligands. This wo k is
di ided in o h ee sec ions. The i s sec ion desc ibes he syn hesis and cha ac e iza ion o he
[W(N
2
)(P
Me2
PP
Ph2
)] complex, which is based on he pen aPod ligand sys em de eloped by
he Tuczek g oup. Al hough his complex showed lowe ca aly ic ac i i y (wi h SmI
2
/H
2
O)
han i s molybdenum-based analogue in e ms o ammonia gene a ion, i is he i s example
o a ungs en-based dini ogen complex ha is able o gene a e o e s oichiome ic amoun s o
NH
3
. A compa ison o he single c ys al s uc u es o he Mo- & W(N
2
) complexes shows
only mino s uc u al di e ences. Elec ochemical and spec oelec ochemical in es iga ions
we e ca ied ou o de e mine he cause o he di e en ca aly ic ac i i ies. I was ound ha
he complexes exhibi la ge di e ences in e ms o hei s abili y in he oxidized s a e.
In he second pa o his wo k, CO is used as a ligand ins ead o N
2
. Ca bon monoxide is
isoelec onic o dini ogen, bu ends o o m mo e s able complexes, which allows o he
in es iga ion o he coo dina ion beha io o ligand sys ems. The coo dina ion beha io o
iden a e PN
Ph
P
R
ligands (R = Ph
2
, E
2
, Cyp
2
,
i
P
2
, Cy
2
) o he Mo(CO)
3
agmen was
in es iga ed. I was ound ha all ligands coo dina ed in a acial geome y, al hough DFT
calcula ions show ha a me idional geome y would be p e e ed o s e ically demanding
esidues. These esul s a e in con as o [Mo(CO)
3
PN
H
P] complexes epo ed in li e a u e,
which do show a me idional geome y o phosphine dono s wi h s e ically demanding sub-
s i uen s. DFT s udies using [Mo(CO)
2
PN
R
P
Me
] (R = N, Ph) complexes showed, ha among
o he hings, he ansi ion s a e o he PN
Ph
P
Me
con aining complex is ene ge ically highe ,
due o he o ma ion o agos ic hyd ogen bonds.
In he hi d pa o his wo k, iden a e ligand sys ems we e in es iga ed o possible deposi-
ion on a gold su ace. Va ious app oaches we e chosen o his pu pose, wi h he main ocus
on he syn hesis o a [Mo(CO)
3
PN
Ph
P
Ph
] complex, which was modi ied wi h a hio g oup in
he pa a-posi ion o he N-dono , in ended o se e as an ancho g oup o he su ace. The
in oduc ion o he selec ed SCN g oup p o ed o be he g ea es challenge, as B
2
is eleased
in he cou se o his eac ion, which oxidized he phosphines. P o ec ing he phosphines wi h
bo ane g oups ul ima ely allowed he in oduc ion o he SCN g oup. Un o una ely, he
desi ed ligand could no be ob ained because oxygen impu i ies in he mo pholine oxidized he
phosphines when a emp ing o emo e he bo ane g oups. Ne e heless, he p esen ed ou e
appea s o be a p omising me hod o he p epa a ion o he PN
Ph-SCN
P
Ph
ligand, which
could subsequen ly be used o coo dina ion o [Mo(CO)3(ch )].
VII
Chap e 2 Scien i ic Backg ound
The amoun o ene gy elease e en inc eases wi h ising empe a u es leading o a alue o
∆
RH
o -109 kJ/mol a 500 °C.
[31]
Following Le Cha elie s p inciple he equilib ium changes
in a o o ammonia by inc easing he p essu e. In he indus ial p ocess usually a ound
200-300 ba o p essu e a e applied.
[12,30,31]
The educ ion in olume shi s he eac ions
equilib ium owa ds he p oduc side, inc easing he yield om 0.13 ol.-% o 17.6 ol.-%.
Depending on he con ac ime be ween he ca alys and he syn hesis gas his yield can a y
and yield lowe amoun s, ye be mo e economical o a company due o as eac ion imes.
[30]
Bo h Habe (1919) and Bosch (1931) we e awa ded he Nobel p ize o hei accomplishmen s.
In 2007 ano he Nobel p ize was awa ded in ela ion o he Habe -Bosch p ocess. This ime
i was gi en o Ge ha d E l o elucida ion o he mechanism on he ca alys s su ace.
[32]
The eac ion is usually di ided in o se e al s eps. The i s s ep is he physiso p ion o
dihyd ogen and dini ogen on he i on su ace, ollowed by he dissocia i e o ma ion o i on
ni ide species.
[30,32,33]
The dissocia i e chemiso p ion was iden i ied as a e limi ing s ep
o he indus ial ammonia syn hesis as sugges ed by Emme .
[34]
As a consequence o he
elec onic p omo o s in he ca alys his eac ion is no only exo he mic bu lowe s he e y
high ac i a ion ene gy ha would be associa ed wi h a eac ion in he gaseous phase.
[30,33–36]
In e es ingly, he dissocia ion o he dihyd ogen molecule seems ba ie less and is he e o e
o en neglec ed in discussions.[37]
Fig. 2.1:
Ene gy diag am o he con e sion om N
2
and H
2
o NH
3
. The blue eac ion pa hway
desc ibes he eac ion on he ca alys s su ace, he ed pa h he di ec eac ion in he gaseous
phase. Adap ed om.[36,37]
The dissocia i e mechanism o he dini ogen molecule can be sepa a ed in o h ee s eps. In he
i s s ep he dini ogen molecule is bound in an end-on ashion o he
α
-i on. Upon ansi ion
o a side-on coo dina ion mode he bonds be ween he ni ogen a oms a e weakened.
[38,39]
Ul ima ely, his leads o homoly ic dissocia ion o he N
≡
N bonds and he o ma ion o
su ace ni ides. Al hough ende gonic, chemiso p ed hyd ogen ge s added sequen ially. These
4

2.2 Biological Ni ogen Fixa ion
eac ion s eps a en’ limi ing as he hyd ogen has a high mobili y on he su ace and he
ene ge ic equi emen s a e easily o e come by he eac ion empe a u e.
[30,36,37]
A e a ound
a cen u y o indus ial ammonia syn hesis, he Habe -Bosch p ocess e ol ed o one o he
mos impo an chemical p ocesses wi h ammonia being one o he mos ly p oduced chemicals
wo ldwide.
[40]
None heless, he p ocess and especially he gene a ion o hyd ogen gas a e
no only e y ene gy-in ensi e, bu also high in expendi u e o esou ces.
[22,41]
Fu he mo e,
he emission o ca bon dioxide is high, especially in iew o he challenges posed by clima e
change. Fo hese easons, a lo o esou ces a e in es ed in imp o ing he p ocess wi h new
ca alys s
[7,42]
o inding ways o elec ochemically gene a e ammonia o which he ene gy
needed can be ob ained om enewable sou ces.
[22,43,44]
The ammonia con aining e ilize s
a e an impo an ac o conce ning c op yields and he e o e o humani y. Ye na u e has
ound a di e en way o access and con e a mosphe ic ni ogen o ammonia. This p ocess is
called biological ni ogen ixa ion.
2.2 Biological Ni ogen Fixa ion
2.2.1 The Ni ogen Cycle
Ni ogenous compounds a e essen ial o plan g ow h, ye hey a e unable o p oduce he
needed compounds hemsel es. Ce ain mic oo ganism on he o he hand a e able o con e
a mosphe ic dini ogen in o ammonia. The con e sion o dini ogen o ammonia is he
i s s ep in he ni ogen cycle (Figu e 2.2), which desc ibes he ixa ion, con e sion and
he e- elease o ni ogen in na u e.
[14,45,46]
The ni ogen cycle can be sepa a ed in o h ee
main s ages. The i s s age is he biological ni ogen ixa ion (BNF) in which a mosphe ic
dini ogen is con e ed in o bioa ailable compounds by mic oo ganisms.
[13,14,46]
The ixa ion
and he mechanisms will be discussed in mo e de ail in sec ion 2.2.2. The second s age o
he ni ogen cycle is called ni i ica ion. The ammonia gene a ed by ni ogen- ixing bac e ia
is ei he assimila ed by plan s o u he oxidized by communi ies o bac e ia gene a ing
ni a e.
[46,47]
Ammonia-oxidizing bac e ia and ni i e-oxidizing bac e ia con e he ammonia
o ni a e ia hyd oxylamine and ni i e.
[48–50]
These eac ions a e an ene gy sou ce as well
as g ow h ac o o he bac e ia.
[48,49,51]
This leads o ammonia and ni a e being he wo
p edominan ni ogen species in he soil.[52]
Deni i ica ion, i.e. he deg ada ion o ni ogen species, is he hi d and inal s ep in he
ni ogen cycle. Du ing his s ep ni a e is educed o molecula ni ogen and eleased back in o
he a mosphe e. This is done by sequen ial educ ion o he ni ogen a om.
[53,54]
The ni a e is
educed o ni i e which in u n is educed o ni ic oxide. The ni ic oxide is hen con e ed
o ni ous oxide and a e a inal educ ion s ep dini ogen is o med.
[53,54]
Each o hese s eps
is pa o an anae obic espi a o y chain and equi es i s own enzyme as a ca alys .
[53–55]
A
5
Chap e 2 Scien i ic Backg ound
inal p ocess o men ion is he dissimila o y ni a e ammoni ica ion in which he ni a e is
no educed o
N2
bu o
NH4+
ins ead. This espi a ion eac ion is no as e icien as he
deni i ica ion because he ene gy gain is less compa ed o he elease o a dini ogen molecule.
Due o his eason he ammoni ica ion is mos ly used as ene gy conse a ion me hod.
[54,56]
No only plan s and bac e ia a e pa o he ni ogen cycle. E e y li ing o ganism akes
pa in i , ye he e is an inc easing an h opogenic in luence due o ex ensi e e iliza ion,
combus ion o ossil uels, bu ning o biomass o domes ica ion o animals.
[13,45]
Due o he
success o he Habe -Bosch p ocess and he a ailabili y o e ilize s, abou hal o all ni ogen
species in o ganic ma e can be aced back o his p ocess while he o he hal esul s om
biological ni ogen ixa ion.[13]
Fig. 2.2:
Simple illus a ion o he ni ogen cycle. The h ee main s ages o he ni ogen cycle a e he
Fixa ion, Ni i ica ion, and Deni i ica ion. Adap ed om[13]
6
2.2 Biological Ni ogen Fixa ion
2.2.2 Biological Ni ogen Fixa ion
In gene al he mic obial binding and con e sion o dini ogen o ammonia om he ai is called
biological ni ogen ixa ion. Simila o he ni ogen cycle i sel , he biological ni ogen ixa ion
can be di ided in o he espec i e ecosys ems in which he associa ed mic obes occu : ma ine,
e es ial and eshwa e sys ems.
[57–59]
Depending on he ecosys em di e en mic obes a e
he main p o agonis s. Ma ine ni ogen ixa ion is mainly associa ed wi h cyanobac e ia (e.g.
T ichodesmium and Richelia).
[57,60–62]
Te es ial ni ogen ixa ion is he second impo an
ield o s udy conce ning ni ogen ixa ion. The mos p ominen o ganism being Azo obac e
inelandii. This mic oo ganism was disco e ed in 1903 and has since been he ocus o esea ch
ela ed o biological ni ogen ixa ion.
[63]
Fu he mo e, i was used o isola e and in es iga e
he s uc u e o he enzyme enabling i s ni ogen ixa ing capabili ies - he ni ogenase (see
sec ion 2.3).
[64,65]
Unlike he ma ine and e es ial ecosys ems, he e ha e no ye been
ex ensi e s udies on ni ogen ixa ion in eshwa e and was long conside ed i ele an .
[59]
Due o ha eason no much is know, ye some ni ogen ixa ing species like he eshwa e
cyanobac e ium Anabaena a iabilis ha e been s udied.
[15,59,66,67]
All a o emen ioned species
a e diazo ophs meaning hey use
N2
as ni ogen sou ce in o de o g ow. In con as o
he Habe -Bosch p ocess, he biological ni ogen ixa ion is pe o med unde physiological
condi ions and al hough a conside able amoun o biochemical ene gy in o m o ATP is
equi ed (e.g. om pho osyn hesis in cyanoba e ica), he eac ion is mo e e icien in he
ni ogenase compa ed o he indus ial he e ogeneous ca alysis.
[66]
Besides he ATP as ene gy
sou ce, eigh p o ons and elec ons a e equi ed o he con e sion o dini ogen o ammonia.
The enzyma ically ca alyzed eac ion is as ollows:[18]
N2+ 8 H++ 8 e−+ 16 MgAT P Ni ogenase
−−−−−−−−→ 2NH3+H2+ 16 MgADP + 16 Pi(2.2)
2.2.3 Ni ogenase
Ni ogenase was isola ed o he i s ime in 1966 by Bulen and LeCom e, bu i ook
ano he 45 yea s be o e he s uc u e could be ully elucida ed wi h he iden i ica ion o he C
4-
ca bide in he cen e o he ac i e si e.
[64,68–70]
The e a e mul iple iso o ms o he ni ogenase.
The mos common and bes s udied is he molybdenum ni ogenase. Due o ha eason, his
sec ion will ocus on he Mo-Ni ogenase only. Al e na i e o ms include a anadium and
an i on ni ogenase.
[15–17]
These o ms a e exp essed unde molybdenum limi ing condi ions
and a e much mo e ine icien compa ed o he molybdenum con aining ni ogenase.
[16,17]
The ni ogenase complex consis s o h ee p o ein uni s: he
α2β2
-he e o e ame called
he dini ogenase (MoFe-p o ein) and wo uni s o he dini ogenase educ ase (Fe-p o ein)
- one on each end. Two clus e s can be ound in each
αβ
-subuni o he ni ogenase. The
i s one is a
Fe8S7
-clus e (P-clus e ), which is in ol ed in he elec on ans e om he
7
Chap e 2 Scien i ic Backg ound
Fig. 2.3:
Ribbon diag am o he Ni ogenase enzyme complex. Loca ed wi hin he MoFe-p o ein
(ligh blue & pu ple) a e wo uni s o he FeMoco and he P-clus e . On bo h ends o he
MoFe p o ein binds he dini ogenase educ ase also called Fe-p o ein (gold & sil e ). The
ac i e componen s wi hin he Fe-p o ein a e he F-clus e as well as 2 MgATP. This image
was c ea ed using PDB en y 1N2C and Chime aX.[71–73]
dini ogenase educ ase o he ac i e si e o he enzyme. The P-clus e is composed o wo
Fe4S4
uni s, bu he ou h sul u a om o each subuni is spli , so he e a e only se en sul u
a oms in he comple e clus e (see Figu e 2.4B). The eac ion shown in eqn. 2.2 akes place
a he ac i e cen e o he dini ogenase. The ac i e cen e is an i on-sul u clus e wi h an
addi ional molybdenum, hence he name: I on-Molybdenum-co ac o (FeMoco, see Figu e
2.4A). The FeMoco is composed o a molybdenum, se en i on, nine sul u and a e y a e
ca bidic ca bon a om as well as a coo dina ing homoci a e molecule. Each o he i on a oms
is coo dina ed by h ee sul u a oms. Six o he se en i on a oms also bind o he ca bidic
ca bon a om in he cen e o he clus e , while he se en h i on a om sa u a es he emaining
coo dina ion si e wi h he sul u o a cys eine. The molybdenum is ound in an oc ahed al
geome y, binding h ee sul u a oms a homoci a e and comple ed by a his idine. The clus e
was i s isola ed in 1977, ollowed by he i s s uc u al models in 1978 and he i s c ys al
8
2.2 Biological Ni ogen Fixa ion
s uc u e 1992.
[74–77]
The s uc u e e ealed by he c ys allog aphy showed an unexpec ed
s uc u e o he FeMoco as i appea s o ea u e a hole in he cen e .
[77]
Technical p og ess
made i possible o eco d X- ay spec a wi h highe esolu ion, which showed a ligh a om in
his e y hole.
[78]
I ook 19 yea s om he publica ion o he c ys al da a o he elucida ion
o he comple e s uc u e wi h he iden i ica ion o he ca bidic ca bon in he cen e o he
clus e . This missing puzzle piece was ound by Lancas e e al. and Spa zal e al. and
esul ed he s uc u e displayed in Figu e 2.4A.[74,79,80]
Fig. 2.4:
S uc u e o he ac i e si e o he Ni ogenase - he i on-molybdenum co ac o (A), he
P-clus e wi h su ounding aminoacids (B) and he F-Clus e (C) o he dini ogenase
educ ase. I on is shown in o ange, sul u in yellow, ca bon in g ay, ni ogen in blue, oxygen
in ed and he molybdenum in ligh blue. This image was c ea ed using PDB en ies 1N2C,
3U7Q and Chime aX.[71–73,80]
Loca ed be ween he FeMoco and he Fe-p o ein is he P-clus e , which is necessa y o he
elec on ans e and he educ i e unc ion o he enzyme.
[81,82]
The elec on is ans e ed o
he P-clus e om he [
Fe4S4
]-clus e (F-clus e , Figu e 2.4C) which is loca ed a he in e ace
be ween he dini ogenase and dini ogenase educ ase.
[82]
Wi hin he dini ogenase educ ase
he [
Fe4S4
]-clus e is embedded in o he s uc u e ia ou cys einyl esidues wo o which
a e p o ided by each
γ
-chain.
[83,84]
Wi hin he dini ogenase educ ase wo binding si es o
MgATP can be ound. The MgATP plays a i al ole in he mechanism in he subs a e
educ ion ac i i y o he ni ogenase.
[85,86]
No only is i a sou ce o ene gy o he eac ion,
bu he binding esul s in s uc u al changes wi hin he p o ein uni ha allow he eac ion
o occu .[81,83]
9

Chap e 2 Scien i ic Backg ound
2.2.4 Mechanism o Ni ogenase
The elucida ion o he s uc u e o ni ogenase ook se e al decades, bu he s uc u e is no
he only aspec ha conce ns esea che s. The mechanism o enzyma ic
N2
- o-
NH3
con e sion
has been he ocus o in es iga ion o almos as long and is s ill no ully unde s ood.
The i s desc ip ion o he mechanism was pos ula ed by Tho neley and Lowe a e
pe o ming a se ies o kine ic measu emen s.
[87–90]
The model uni ies assump ions de i ed
om model sys ems p epa ed in he con ex o syn he ic ni ogen ixa ion wi h kine ic
expe imen s.
[87,89,91]
Cha s a ed ha dihyd ogen coo dina ed o a me al cen e can be
displaced by dini ogen unde educ i e condi ions and ha con e sion o ammonia occu s
h ough successi e p o ona ion and single-elec on educ ion s eps.
[89,91]
As seen om eqn. 2.2
one equi alen o hyd ogen is p oduced wi h each u no e o he ca aly ic cycle. The ca aly ic
cycle desc ibed in he Tho neley-Lowe-model is di ided in o eigh dis inc one-elec on
s eps (Figu e 2.5B). The elec ons needed o he ca aly ic cycle s em om ano he cycle
which is in e wined wi h he cycle o he FeMoco. The wo mechanism a e he cycle o
he Fe-p o ein (Figu e 2.5A) which ans e s he elec ons o he FeMoco and he ca aly ic
cycle i sel in which ammonia is gene a ed (Figu e 2.5B). Du ing he Fe-p o ein cycle he
clus e is ound in wo oxida ion s a es. The oxidized and he educed o m in which he
clus e is ound in he oxida ion s a es 1+ and 2+ espec i ely.
[92]
Be o e associa ion and
elec on ans e o he MoFe-p o ein wo ATP molecules bind o he p o ein, changing i s
s uc u al a angemen .
[93]
This change in he con o ma ion has mul iple e ec s he i s
being he abili y o associa ion o Fe- and MoFe-P o ein.
[93–95]
In he cou se o he s uc u al
changes, he F-clus e is also o a ed close o he in e ace be ween he p o eins, b inging i
wi hin Van de Waals each o he P-clus e .
[93]
As he i on p o ein is he only known elec on
sou ce o he educ ion and only one elec on can be ans e ed om a p o ein uni , he
dini ogenase educ ase cycle in ol es associa ion and dissocia ion a e e e y single-elec on
ans e .
[92,93]
Compa ing expe imen al esul s ying o de e mine he o de o eac ion
s eps in he associa ed s a e o he p o eins se e al disc epancies a ise.
[94]
Depending on
he me hod di e en a e cons an s we e de e mined. Fu he mo e, he ex emely sensi i e
p o ein complex and i s en i onmen -dependen p ope ies cause de ia ions and di e ences in
he expe imen s, espec i ely.
[94,96–102]
Independen o he o de o e en s conce ning ATP
hyd olysis and elec on ans e , phospha e is eleased a e he elec on ans e and he
p o ein complex dissocia es. The hyd olysis o MgADP e e ses he p e ious con o ma ional
change and hus p e en s he p econdi ion o he assembly o he Fe- and MoFe-p o eins.
[96]
10
2.2 Biological Ni ogen Fixa ion
Fig. 2.5:
Illus a ion o he Tho neley-Lowe-model desc ibing he ca aly ic cycle o he biological
ni ogen ixa ion. Each s ep o he cycle is ep esen ed by an E wi h an index e lec ing he
numbe o elec ons ans e ed. PDB en ies 1N2C
[71]
and 3U7Q
[80]
we e used o c ea ing
he MoFe-, Fe-p o ein and e edoxine (PDB 1FRI) images in he i on cycle. Adap ed om
Einsle and Rees.[89]
In he oxidized o m he Fe-p o ein de aches om he MoFe-p o ein and can be egene a ed
by educ ion. Upon educ ion he MgADP is also exchanged wi h wo MgATP molecules,
allowing he cycle o s a again. Fo each s ep, deno ed E in Figu e 2.5B, he ni ogenase and
dini ogenase educ ase mus associa e and dissocia e.
[103]
Besides he ongoing in es iga ions
conce ning he o de o e en s as well as he kine ics, de e mina ion o he a e limi ing s ep
is s ill pa o cu en discussions in li e a u e.[89,94]
The second pa o he mechanism is he ni ogen educ ion i sel . He ein, wo pa s mus
11
Chap e 2 Scien i ic Backg ound
be conside ed du ing he cycle in he MoFe p o ein: The elec on ans e ia he P-clus e
and he eac ions a he ac i e si e o he enzyme. As desc ibed abo e, he ca aly ic cycle
o he MoFe-p o ein is di ided in o eigh s eps (E
0
-E
7
) ollowing he Tho neley-Lowe-
model.
[88–90,104,105]
In he i s h ee s eps (E
0
-E
3
) ou educ ion equi alen s a e accumula ed
as b idging hyd ides be ween he i on a oms in he FeMoco.
[104–107]
The addi ional wo p o ons
a e bound o sul u a oms.
[104]
The exac s uc u e o he educed s a e o he ac i e si e is o
da e no know o ce ain as he calcula ed ene ge ics o he clus e show massi e a ia ions
depending on he DFT me hod chosen.
[104,108,109]
The key in e media e o he cycle is ound
in he E
4
s age which is also called he Janus-In e media e. In his s ep, he
N2
subs a e
is bound o he FeMoco. The exac na u e o his s ep is no ye ully unde s ood and
di e en app oaches including an ac i e ole o he homoci a e ligand as a ansi ional p o on
s o e as well as displacemen o he bel sul u s has been discussed.
[110,111]
Wha is known
is he ac ha he E
4
s age can eac in wo di e en di ec ions: back owa ds he es ing
s a e E
0
o con inue o p o ona e and educe he
N2
.
[89,105]
Con inuing he pa h owa ds
gene a ion o ammonia, wo gene al mechanisms a e p oposed: a dis al and an al e na ing
pa hway.[107,112,113]
Fig. 2.6: Schema ic ep esen a ion o he al e na ing and dis al mechanism o ni ogenase.[107,113]
In he dis al pa h, he e minal ni ogen is i s p o ona ed/ educed and hen, a e he
o ma ion o a ni ido species, he second equi alen ammonia is gene a ed.
[107,113]
This
model is also discussed as mechanism in Cha - ype ca alys s in syn he ic ni ogen ixa ion (c .
sec ion 2.3.1). The second pa hway is he al e na ing mechanism. Unlike he dis al mechanism,
in he al e na ing mechanism, he ni ogen a oms a e al e na ely p o ona ed/ educed and he
wo equi alen s o ammonia a e eleased in he las wo s eps o he cycle.
[107,113]
Al hough
12
2.3 Syn he ic Ni ogen Fixa ion
no ye ully p o en, he al e na e pa h seems o be mo e likely. In addi ion o expe imen al
de ec ion o hyd azine and diazene unde ca aly ic condi ions, hese compounds can also be
used as subs a es o he gene a ion o ammonia by ni ogenase.[107,114–116]
2.3 Syn he ic Ni ogen Fixa ion
Inspi ed by na u e, syn he ic ni ogen ixa ion deals wi h he con e sion o dini ogen o
ammonia using ansi ion me al complexes. In es iga ions o he p ope ies o hese simple
model sys ems and hei ca aly ic abili y will p o ide impo an clues o he mechanism o
ni ogenase. O e he decades, howe e , syn he ic ni ogen ixa ion has de eloped in o a b oad
b anch o esea ch in coo dina ion chemis y, which, in addi ion o s udying di e en sys ems
and hei eac i i y as well as de eloping new ca aly ic pa hways, is also conce ned wi h
undamen al ques ions o coo dina ion chemis y.
[19,20,89,117,118]
The ounda ion o syn he ic
ni ogen ixa ion was laid by Allen and Seno (1965) wi h he syn hesis o he i s complex
bea ing a dini ogen ligand and a u henium cen e ([Ru
(N2)(NH3)5
]X
2
; X = B , I, BF
4
,
PF
6
).
[119]
Addi ion o NaBH
4
o he complex wi h iodine coun e ions also gene a ed he
i s amoun s o ammonia.
[119]
The i s complex coo dina ing a dini ogen om ni ogen
a mosphe e was epo ed wo yea s la e .
[120]
The coo dina ion o a dini ogen ligand is
obse ed by in a ed spec oscopy as he coo dina ion o he dini ogen causes a shi o
lowe wa enumbe s compa ed o ee
N2
molecule.
[117]
This shi is commonly e e ed o as
ac i a ion. The u he he
N2
s e ch is shi ed o smalle wa enumbe s, he s onge he
dini ogen ligand is ac i a ed wi h ega d o de i a iza ion.
[21,121]
The cause o he shi is
ound in he change o he N
≡
N bonds due o he coo dina ion o he me al cen e . The
o ma ion o a bond be ween he me al cen e and he ni ogen leads o an elec on densi y
ans e , which is desc ibed by he Dewa –Cha –Duncanson model.
[122]
A i s elec on
densi y is ans e ed om he ni ogen o he me al cen e , known as
σ
-dona ion, ollowed by
a
π
-backdona ion, in which elec on densi y is ans e ed om he me al cen e back o he
ligand (Figu e 2.7).[123–125]
13
Chap e 2 Scien i ic Backg ound
2.3.3 Sys ems o Pe e s’ g oup
Al hough i on is mainly discussed o be he ac i e si e o he ni ogenase, syn he ic ni ogen
ixa ion mos ly e ol es a ound molybdenum and ungs en complexes. The Pe e s g oup
se ano he impo an miles one as hey p esen ed he i s i on based ca alys capable
o
N2
- o-
NH3
educ ion, using an i on dini ogen complex bea ing he is[o-(diisop opyl-
phosphino)phenyl]bo ane ligand (P3B, Figu e 2.12 le ).[166]
Fig. 2.12:
I on dini ogen complexes bea ing he a ia ions o he ligand o syn he ic ni ogen ixa ion
de eloped by Pe e s e al.[166,167]
Addi ion o HBA
F
and
KC8
yielded 7 equi alen s o ammonia.
[166]
The amoun o ammonia
was inc eased d as ically ( o 64 equi .) by inc easing he amoun p o on- and elec on
sou ces.
[167]
Fu he op imiza ion and addi ional i adia ion o he solu ion inc eased he
ammonia yield again o 94 equi alen s.
[168]
Unlike he eac ions p esen ed by Cha and
Sch ock, his ca alysis is no ca ied ou unde ambien condi ions, bu a a empe a u e
o -78 °C. Exchanging he educing agen as well as he acid wi h less po en compounds
(
[Ph2NH2]OT
and
Cp2*
Co) a yield o 89 equi alen s o ammonia we e gene a ed - s ill using
he p esen ed i on sys em.
[169]
The peculia i y o his combina ion lies in he ans e mode o
he p o ons and educ ion equi alen s as he combina ion o he
Cp2*
Co wi h he acid ac s as
PCET eagen (PCET = P o on Coupled Elec on T ans e ).
[169]
This insigh was used as a
s a ing poin owa ds elec oca aly ic ni ogen ixa ion, which he g oup demons a ed in
2018 using [
Cp2*
Co]
+
, [
Fe(N2)
(
P3B
)]
-
and anilinium acids in con olled po en ial elec olysis
expe imen s. In his way, 6.7 equi alen s o ammonia could be gene a ed.
[170]
The main issue
o elec oca aly ic ammonia gene a ion is he compe ing hyd ogen e olu ion eac ion which is
o en domina ing.
[169,170]
Ea ly, ye unsuccess ul a emp s used a me cu y pool elec ode as
he o e po en ial o me cu y allows mo e nega i e po en ials.
[152,171,172]
In 2022 he g oup
ound an al e na i e app oach owa ds elec oca alysis by employing a media o complex ha
accep s he elec ons om he ca hode and ans e s hem as a PCET agen o he ac ual
ca alys (Figu e 2.13).[173]
20

2.3 Syn he ic Ni ogen Fixa ion
Fig. 2.13:
Illus a ion o he PCET media ed elec ochemical
N2
- o-
NH3
educ ion by Pe e s e al.,
exempli ied wi h a ungs en bisdini ogen complex. Edi ed a e .[173]
A numbe o ca alys s we e in es iga ed using his app oach, wi h he bes p oducing 40 equi .
o ammonia.
[173]
In e es ingly, he bes ca alys was ound o be he e y complex employed
in he o iginal expe imen s by Picke and Talamin in 1985. In he same yea he g oup
could also demons a e di ec elec oca alysis on a py idine based pince sys em. S a ing
om he well known
[MoB 3(PNP Bu)]
complex 11.7 equi .
NH3
we e gene a ed.
[174]
These
imp essi e esul s we e achie ed by e y conscious selec ion o he componen s in ol ed.
Pa allel o he e o s in es ed in o he [
Fe(N2)
(
P3B
)]
-
complex he Pe e s g oup also
in es iga ed he in luence o he dono ans o he dini ogen ligand by syn hesizing wo
a ian s o he
P3B
ligand. The bo on was exchanged by ca bon (
P3C
) (Figu e 2.12 middle) as
well as silicon (
P3Si
) (Figu e 2.12 igh ).
[167]
Howe e , he ca aly ic ac i i y o he co esponding
i on complexes was lowe han ha o he [
Fe(N2)
(
P3B
)]
-
complex. 47 equi . o ammonia
we e ound o he [
Fe(N2)
(
P3C
)]
-
complex, while [
Fe(N2)
(
P3Si
)]
-
gene a ed only 4.4 equi .
[167]
No only a ia ions o he ligands we e in es iga ed bu also di e en me al cen e s. Using he
leas ac i e
P3Si
ligand low alen dini ogen complexes wi h osmium and u henium cen e s
we e syn hesized.
[175,176]
Using la ge amoun s o
[Ph2NH2][OT ]
(1500 equi .) and
Cp2*
Co
(1800 equi .) he osmium complex was able o gene a e 120 equi alen s o NH3.[176]
21
Chap e 2 Scien i ic Backg ound
2.3.4 Sys ems o he Nishibayashi g oup
The Nishibayashi g oup ocuses on pince based sys ems. Pe de ini ion pince ligands a e
igid ligands ha en o ce a me idional coo dina ion geome y.
[177]
No only hei a iabili y,
bu also hei o en high ca aly ic ac i i y has inc eased in e es in pince -based sys ems in
ecen decades.
[178–180]
The ca aly ic ac i i y is o en ela ed o he igidi y and high he mal
s abili y o he complexes allowing well de ined ca aly ic eac ions.
[179–183]
Al hough he e m
pince is now used in a b oadened sense om i s o iginal de ini ion, i usually e e s o a
iden a e sys em wi h 3 dono a oms. O en, amines in he o m o py idines o ca benes
a e ound a he cen al posi ion. Typical g oups o linkage a e amines o
CH2
-g oups bu
also silicone g oups a e well known modi ica ions.
[182–185]
The Nishibayashi g oup u ilizes
pince ligands o de elop e y ac i e ca alys s o syn he ic ni ogen ixa ion. The i s
sys em p esen ed by he g oup capable o ca aly ic
N2
educ ion was an end-on b idged
binuclea molybdenum complex bea ing a PNP pince wi h P
Bu
2
dono s on each cen e
(Figu e 2.14B). The ligand sphe e was comple ed by wo mo e
N2
ligands on each molybdenum
(Figu e 2.14A).
[186]
The bes esul s we e achie ed by addi ion o [Lu H][OT ] and Cp
2
Co
wi h 23.2 equi . o ammonia we e gene a ed pe dinuclea complex.
[186]
Based on hese ini ial
esul s, he PNP pince ligand was modi ied by a ia ion o he subs i uen s on he phosphine
dono s and in he pa a-posi ion o he py idine.
[187,188]
Va ia ion o one o he phosphines, and
he eby c ea ing asymme ic ca alys s, did no inc ease he amoun o ammonia gene a ed,
[187]
bu in oduc ion o di e en g oups on he py idine ing inc eased he ni ogen con e sion up
o 34 equi . wi h a me hoxy g oup.
[188]
This could be imp o ed again (52 equi .
NH3
) by
inc easing he added p o ons and educ ion sou ces. A compa able esul wi h 31 equi . was
ound o he 4-me hyl-py idine.
[188]
In 2015 he sys em was modi ied again by exchaning he
me hoxy g oup by a e ocene moie y, which could gene a e wo equi alen s mo e unde he
same condi ions as he me hoxy sys em.
[189]
Besides he PNP pince and i s modi ied a ian s,
he g oup also p esen ed esul s e ol ing a ound a PCP pince wi h a N-he e ocyclic ca bene
(NHC) as cen al dono .
[190]
Using he [Mo(
N2
)
2
(PCP)
2
(
µ
-
N2
)] complex and la ge amoun s
o [Lu H][OT ] and [Cp
2*
Co] (1920 and 1440 equi .) he complex gene a ed 230 equi . o
ammonia.[190]
22
2.3 Syn he ic Ni ogen Fixa ion
Fig. 2.14:
Selec ion o complexes used o syn he ic ni ogen ixa ion by Nishibayashi e al.
[186,190–192]
The dinuclea sys ems we e no he only ones in he scope o he Nishibayashi g oup. Using
he PNP
Bu
pince ligand and s a ing om
[MoCl3( h )3]
hey gene a ed he ni ido complex
[MoNCl(PNP)]
(Figu e 2.14C), which was also ca aly ically ac i e owa ds
N2
educ ion. Using
his complex, [Lu H][OT ] and Cp
2
Co a o al o 6.6 equi . o ammonia we e gene a ed.
[191]
This ype o ni ido complex was also ob ained by use o a iden a e iphosphine ligand,
whose ca aly ic ac i i y was signi ican ly highe in compa ison.
[192]
The ligand is composed o a
cen al phenyl phosphine which is connec ed o wo e minal di- e -bu yl phosphine g oups ia
e hyl b idges (Figu e 2.14D). Addi ion o Cp
2*
Co (540 equi .) and 2,4,6- ime hylpy idinium
i la e ([ColH][OT ], 720 equi .) yielded a o al o 63 equi . o ammonia.
[192]
Use o hese wo
eagen s as p o on and elec on sou ce, while s a ing om he molybdenum(III) p ecu so
[MoI3( h )3
], in combina ion wi h hei well es ablished PNP pince , hey managed o ob ain
a s agge ing amoun o 415 equi . o ammonia.[193]
A majo b eak h ough was p esen ed ha shows pa allels o he wo k o Pe e s e al. As
ound o he i on sys ems, using a PCET agen g ea ly imp o ed he ca aly ic ac i i y o he
a o emen ioned pince sys ems. The PCET agen used is a combina ion o sama ium diiodide
and wa e o simple alcohols such as me hanol, e hylene glycol o e hanol.
[194]
Using 180 equi .
o
SmI2
and e hylene glycol he
[MoI3(PNP)]
complex bea ing wo P
Bu
2
g oups gene a ed
42.8 equi . o ammonia while he co esponding ni ido complex gene a ed 50.0 equi . Fo he
end-on b idged dini ogen complex bea ing he NHC pince ligand his combina ion gene a ed
53.3 equi . o ammonia.
[194]
The mononuclea ichlo ido molybdenum complex bea ing his
NHC pince yielded 4350 equi . o ammonia upon eac ion wi h
SmI2
/
H2O
(14400 equi alen s
each). This e ec i e ca alys is he i s sys em o use wa e as p o on sou ce o gene a e
ammonia.
[194]
The use o wa e p oo ed o yield la ge amoun s o ammonia compa ed o he
small alcohols. In 2023 he g oup p esen ed a ichlo ido molybdenum complex bea ing a
23
Chap e 2 Scien i ic Backg ound
modi ied PCP (simila o Figu e 2.14 A, wi h R = CF
3
& H), which is e en mo e ac i e and
gene a ed 60.000
±
4300 equi . o ammonia pe Mo.
[195]
The di e ence in eac i i y is e y
well exp essed by he use o classical Cha ype complexes which unde p o ic and educ i e
condi ions we e no ca aly ically as hey ace some p oblems du ing he ca aly ic cycle (c .
sec ion 2.3.1). Applica ion o he
SmI2
/
H2O
allowed o ca aly ic ammonia gene a ion using
hese simple molybdenum complexes.
[196]
No ably, he eac ion pa hway is expec ed o di e
om he Cha cycle desc ibed abo e. The ans-
[Mo(N2)2(PMe2Ph)4]
complex esul ed
40 equi . o ammonia while he in si u gene a ed complex wi h wo equi alen s o dpppe
(1,5-bis-(diphenylphosphino)-pen ane) om
MoI3( h )3
esul ed 46 equi .
NH3
. Inc easing
he amoun o PCET agen , his could be scaled o 83 equi . o ammonia.
[196]
The app oach
wi h sama ium diiodide and wa e /alcohols a e he i s condi ions in which a Cha - ype
sys em is capable o ca aly ic ammonia gene a ion. The second example o his is p esen ed
by ou g oup (sec ion 2.3.5).
[197]
In e es ingly, he ungs en analogues we e no ca aly ic
unde hese condi ions.
[197]
In es iga ions conce ning he mechanism a e a majo ocus o he
Nishibayashi g oup. Se e al app oaches based on expe imen al indings and DFT calcula ions
a likely mechanism in ol es a b idged in e media e wi h a dinuclea molybdenum complex ha
spli s he b idging dini ogen ligand in o ni ides.
[197,198]
In o de o gain u he insigh s in o
he mechanism, hey p esen ed a de ailed s udy on he s uc u e o he
SmI2
/
H2O
s uc u es
o med in solu ion.
[199]
O he han p edic ed p e iously, he expe imen al esul s poin owa ds
he o ma ion o sama ium wa e and sama ium h complexes, depending on he amoun o
wa e , wi hou di ec Sm-I bonds.[200]
Besides he molybdenum based sys ems, he g oup also p esen ed se e al s udies in es iga ing
he ac i i y o pince complexes wi h o he ansi ion me al cen e s including i on,
[201]
cobal ,
[202]
ch omium,
[203]
anadium,
[204,205]
henium
[206,207]
and manganese.
[208]
Al hough
he ligands used all belong o he pince ca ego y and he e minal phosphines chosen ba e
Bu
2
subs i uen s, hey we e e y di e en as we e he condi ions used in o de o ob ain
ca aly ic ac i i y. To elabo a e on hese sys em a ew examples will be explained mo e
de ailed. The i on sys em was based on an anionic PCP pince wi h he anionic cen e being
on he cen al benzene. Upon addi ion o 8000 equi . o
KC8
and 7360 equi . o HBA
F
252 equi . o ammonia and 68 equi . o hyd azine we e gene a ed.
[201]
Rhenium complexes
bea ing he py idine based PNP pince o a a ian wi h a sligh modi ica ion in he 4-posi ion
gene a ed be ween 3 and 9 equi . o ammonia wi h 800 equi . o
KC8
and 800 equi . o
[HPCy
3
][BA
F
].
[206]
The cobal sys em was e y di e en as he ammonia was gene a ed
by hyd olysis o a p e iously o med silylamine. A cobal dini ogen complex bea ing he
PNP pince was eac ed wi h 600 equi .
KC8
and
Me3SiCl
. Addi ion o acid yielded a o al
o 44 equi . o ammonia. Scaling his eac ion o 6000 equi . o subs a e, 351 equi . o
ammonia we e ound.[202]
The la es app oach o he g oup in ol es ligh d i en ammonia gene a ion.
[200]
Using a
molybdenum ca alys s (e.g.
[MoI3(PCP)]
) and pho oac i e coca alys s, hey we e able o
24
2.3 Syn he ic Ni ogen Fixa ion
ca aly ically gene a e ammonia upon i adia ion.
[200]
The
[MoI3(PCP)]
complex gene a ed
29.5 equi . o ammonia. This was inc eased by sligh modi ica ion o he ligand. In oduc ion
o a
CF3
-g oup on one side o he benzimidazole backbone inc eased he yield o 41.3
±
6.2
equi . o ammonia.[200]
2.3.5 Sys ems o he Tuczek g oup
The Tuczek g oup ocuses on Cha ype sys ems. As desc ibed abo e he classical Cha
sys ems a e acing wo majo p oblems (c . sec ion 2.3.1). The i s p oblem occu s in
he ni ido s age, whe e he oxida ion s a e o he molybdenum cen e is high, making i
a ha d Lewis acid ha can lead o decoo dina ion o he phosphine dono s. The second
p oblem occu s in he egene a ion o he ca alys s in he las s ep. In addi ion o he desi ed
egene a ion o he ca alys , a disp opo iona ion eac ion occu s ha p oduces inac i e
dihalide complexes.
[21,154]
This side eac ion leads o a ca alys loss o abou 50% wi h each
un o he cycle.
[21,154]
The Tuczek g oup is add essing p ecisely hese wo poin s and
de eloping Cha ype sys ems ha a emp o ci cum en hese p oblems. This is done in
wo ways: supp ession o he disp opo iona ion eac ion by occupa ion o he ans-posi ion o
he dini ogen, which could also enhance he ac i a ion o he ligand, and he decoo dina ion in
he high oxida ion s a es is coun e ac ed by inc easing he s abili y by exploi ing he chela ing
e ec o mul iden a e ligands. A i s wo main s a egies we e pu sued in o de o ul ill
he se goals. The ligands which mee bo h c i e ia o bypassing he p oblems o he Cha
cycle we e cha ac e ized by ipodal o iden a e s uc u al mo i s. The ipodal ligands a e
usually based on ei he an iso-bu yl o neo-pen yl backbone.
[209–211]
The backbone and ipodal
geome y o he ligand en o ces a acial coo dina ion o he ligand. Wi h addi ion o a biden a e
coligand and educ i e condi ions mono-dini ogen complexes we e syn hesized.
[209–211]
Besides
he iso-bu yl and neo-pen yl backbones, ou g oup also succeeded in syn hesizing dini ogen
complexes bea ing a cyclohexane based ipod and a ipodal sys em simila o he neo-pen yl
sys em bu he qua e na y ca bon was subs i u ed by silicon.
[212–215]
Unlike he o he ipodal
sys ems, coo dina ion o he cyclohexyl-based ligand equi es highe empe a u es and eac ion
imes because he dono s mus be o ien ed in he axial di ec ion o coo dina ion, which is
he less a o able con o ma ion.
[212]
The silicon subs i u ed ligand was used o in es iga e he
di e en in luence o alkyl- and a yl-phosphines as dono s. I was ound ha by subsequen
exchange o dia ylphosphine by dime hylphosphine led o an inc ease in ac i a ion o he
N2
ligand.
[212]
Compa ison o he ipod/diphos combina ion bea ing all
PMe2
-dono s o a
mono-dini ogen complex bea ing i e
PMe3
-dono s showed a lowe ac i a ion o he ipodal
complex, illus a ing he e ec o s e ic in luence on ac i a ion.
[213,215]
To gain u he insigh
in o he s e ical aspec simila s udy was pe o med by Söncksen e al. who chose he
iso-bu yl (when mo e han one
iP 2
g oups we e in ol ed) based ipod ligand and sequen ially
subs i u ed diphenylphosphine by he s e ically demanding diisop opylphosphine. In e es ingly,
25

Chap e 2 Scien i ic Backg ound
he inc ease in s e ic demand lead o he o ma ion o he bis-dini ogen complexes whe eas he
complex bea ing only a ylphosphines o med he mono-dini ogen complex.
[210]
A simila s udy
was pe o med bei P eil e al. who p epa ed ligands con aining be ween 1 and 3 phospholano
g oups. Phospholano g oups a e cha ac e ized by di e en beha io as ound om egula
alkylphosphines.
[216–218]
Fo he phospholano ipod - e en wi h h ee phospholano g oups -
he mono-dini ogen complex was ound as long as dppm (diphenylphosphinome hane) was
used as coligand.
[216,218]
The ac i a ion ound o he
N2
ligand in he complex wi h h ee
phospholano g oups is lowe compa ed o i s
PMe2
analogue bu highe han he complex
wi h all diphenylphosphine.
[216]
An impo an way o une he ac i a ion and he eby he
eac i i y owa ds de i a iza ion is ca e ul selec ion o he ans ligand.
[145]
The ac i a ion
should also be inc eased by subs i u ion o he dono in ans-posi ion o he dini ogen
ligand. Coo dina ion o an amine dono ans o he
N2
should inc ease he ac i a ion due o
elimina ion o
π
-accep o p ope ies, hence inc easing he elec on densi y on he molybdenum
and u he weaken he N
≡
N- iplebond.
[219]
Un o una ely, he mono-dini ogen complex
bea ing he ipodal ligand wi h wo phosphines and a die hylamine esidue could no be
ob ained, due o he weak coo dina ion beha io o he amine. The p oduc ob ained ins ead
was he bisdini ogen a ian .[219]
Fig. 2.15:
Examples o di e en ni ogen complexes syn hesized by he Tuczek g oup o syn he ic
ni ogen ixa ion.[214,215,218–223]
In addi ion o he ipodal sys ems, he Tuczek g oup also in es iga ed ni ogen complexes
bea ing iden a e and pince ligands.
[145,220,221,224]
Following on om he wo k o Geo ge
e al., who p epa ed ni ogen complexes wi h di e en iden a e ligands, he g oup also
in es iga ed he in luence o di e en subs i uen s on he dono a oms, as well as he in luence
o phosphine and amine dono s in ans posi ion o he dini ogen ligand.
[145,225,226]
The
indings o his g oup ega ding he iden a e sys ems will be discussed in de ail in he
in oduc ion o chap e 4 as i ocuses a ound iden a e PNP ligands.
Ma ying he wo concep s o iden a e and ipodal ligands, a new singula ligand wi h pen-
aphosphine en i onmen eme ged, esul ing in a pen aden a e e apodal ligand (pen aPod).
26
2.3 Syn he ic Ni ogen Fixa ion
This concep no only elimina es he need o an addi ional coligand, bu also inc eases he
chela e e ec e en mo e, s abilizing he co esponding complexes. Fu he mo e i c ea es
a single si e Cha - ype ca alys which would go hand in hand wi h imp o ed elucida ion
oppo uni ies ega ding he mechanism.
The i s gene a ion o he pen aPod (P
2Ph
PP
2Ph
) ea u ed only
PPh2
dono s besides he
phosphine dono linking he ipodal and iden a e pa . Coo dina ion o he ligand o
[
MoCl3( h )3
] u ned ou o be qui e di icul due o he opology o he p ecu so and he
wo possible coo dina ion modes.
[222]
As he Mo(III) complex is in me idional a angemen ,
he iden a e pa is a o ed, which was expe imen ally p o en by EPR spec oscopy. Due
o his p e e ence he complex has o unde go se e e s uc u al changes in o de o om
he desi ed mono-dini ogen complex. I was ound ha upon educ ion se e al species we e
o med some o which appea o be coo dina ion polyme s wi h he ligand in e connec ing
molybdenum cen e s.
[222,227]
Adap ed om he silicon based ipod ligand, a modi ied e sion
o he pen aPod wi h a silicon in he ipodal backbone was syn hesized. Using his app oach
a mono-dini ogen complex was ob ained. Like he ipodal sys ems he esul ing complex
was labile agains acids and due o he di icul syn hesis could no be ob ained in i s pu e
o m.[222]
The p oblems o he i s gene a ion sys em, which we e, among o he hings, due o he insu -
icien eac i i y di e ences o he e minal phosphines, we e esol ed in he second gene a ion
o he pen aPod ligand (P
2Me
PP
2Ph
, Figu e 2.16).
[222]
Subs i u ion o he diphenylphosphine
g oups on he ipod si e by dime hylphosphine in oduced nucleophillic g adien in o he
sys em wi h he
PMe2
g oups, a o ing he acial geome y in he Mo(III) s age and enabling
he isola ion o a mono-dini ogen complex upon educ ion bea ing he en i e pen aPod
ligand.
[222,227]
The [
Mo(N2)
(P
2Me
PP
2Ph
)] complex no only showed he expec ed AA’XX’M
pa e n in he
31
P NMR spec um bu also a e y s ong ac i a ion o he
N2
ligand as can
be seen om he s e ching ib a ion (νNN = 1929 cm-1) in he IR spec um.[222,227]
Fig. 2.16:
The pen aPod concep a ose om combina ion o he iden a e PPP and ipodal PPP
ligands.[222,227]
Al hough he ac i a ion o he
N2
ligand is high and he co esponding hyd azido(2-) complex
was ob ained, he complex did no show any ca aly ic beha io unde condi ions epo ed by
Pe e s e al. o Nishibayashi e al.
[222,223,227,228]
The only sys em ound o be ac i e unde
27
Chap e 2 Scien i ic Backg ound
hese ype o condi ions ound in ou g oup is he PN3P pince sys em epo ed by S ucke
e al., which gene a ed 3.12 equi . o
NH3
using
Cp2*C
and [ColH][OT ] (Figu e 2.17).
[229]
Fig. 2.17:
[Mo
Cl3
(PN
3
P)] complex syn hesized by S ucke capable o ammonia gene a ion
(3.12 equi .) upon addi ion o [
Cp2*C
] and [ColH][OT ]. This is he i s sys em o
he Tuczek g oup which exhibi ed ca aly ic ac i i y.[229]
Al hough he i s a emp s owa ds he ca aly ic ac i i y o he pen aPod sys ems we e no
success ul he de elopmen con inued. Junge e al. succeed in coo dina ing o he P
2Me
PP
2Ph
ligand o Rh and Ru. The esul ing complexes we e used owa ds ac i a ion o small molecules
such as CN–o N3–.[230]
28
Chap e 3
P ojec 1
E en ough a a ie y o di e en combina ions o acids and educing agen s we e es ed, no
success ul ca aly ic gene a ion o ammonia was achie ed un il he p o on coupled elec on
ans e (PCET) app oach p esen ed by Nishibayashi was applied. Using sama ium diiodide
and wa e in h he pen aPod dini ogen complex exhibi ed ca aly ic beha io . Using his
me hod 25.7 equi . o ammonia we e gene a ed.
[231]
To in es iga e he ole o he ligand
as an aspec o he newly disco e ed ca aly ic ac i i y, simila mono-dini ogen complexes
wi h pen aphosphine en i onmen we e syn hesized and es ed owa ds hei ca aly ic ac i i y.
The complexes p epa ed we e a neo-pen yl based ipodal PPP ligand bea ing all e minal
PPh2
g oups wi h a dmpm (dime hylphosphinome hane) coligand and he analogue iden a e
a ian wi h he p PPHP ligand, which is also used as iden a e building block o he
pen aPod ligand. Bo h complexes we e es ed owa d hei ca aly ic ac i i y unde iden ical
condi ions as he pen aPod complex, howe e , only subs ochiome ic amoun s o ammonia
we e ound, p oo ing he e ec i eness o he pen aPod concep .
[231]
The sys em is a single
coo dina ion si e Cha - ype ca alys and one o he main in e media es o he Cha cycle
is he hyd azido(2-) complex, Engesse e al. we e also able o isola e and ho oughly
cha ac e ize he co esponding
NNH2
complex a e p o ona ion wi h HBA
F
.
[231]
In o de
o p o e he ole o he [
Mo(NNH2)
(P
2Me
PP
2Ph
)]BA
F
complex in he ca aly ic cycle, his
complex was also used as ca alys wi h
SmI2
/
H2O
. Due o s abili y issues in he equi ed
sol en , he complex was gene a ed in si u and added o he PCET-agen con aining solu ion.
This app oach yielded 26.1 equi . o ammonia p o ing he hyd azido(2-) s age o be an en y
poin in he ca aly ic cycle.[231]
Cha sys ems do no only in ol e molybdenum bu also ungs en complexes. In ac
he i s sys ems o he Cha - ype complexes ha yielded he bes esul s o ammo-
nia gene a ion (90 %) we e he cis-[
W(N2)2(PMePh2)4
] complex by Cha e al. and he
[W(NNH2)(OTs)(dppe)2]+
complex employed o elec oca alysis by Picke and Tala-
ma in.
[151–153]
Besides molybdenum, ungs en is ano he ansi ion me al o en ound in
syn he ic ni ogen ixa ion. Due o i s impo an ole and he e ec i eness o he pen aPod
concep , combina ion o ungs en and he pen aPod complex is an in e es ing app oach, which
will be he i s p ojec p esen ed in his hesis.
29
Chap e 3 P ojec 1
Aiming a de e mining he ole o he me al in he
desc ibed edox p ocesses, we ca ied ou he same expe i-
men s o [Mo(N
2
)(P
Me2
PP
Ph2
)] (1). CV s udies e ealed se e al
diffe ences compa ed o he W–N
2
complex. Fo ins ance, he
i s oxida ion p ocess a E
1/2
(1) was ound o be no ully
e e sible a low scan a e ( < 0.1 V s
−1
). Mo eo e , a sup-
plemen a y i e e sible anodic peak a E
pa
(3) (ca. −0.7 V s.
Fc
+
/Fc) was de ec ed o < 0.5 V s
−1
(Fig. 5A). Fu he oxi-
da ion a E
pa
(2) was also accompanied by a supplemen a y oxi-
da ion peak a E
pa
(4) which disappea ed a high scan a e
(Fig. 5B). A las and con e sely o complex 2, he Mo complex
displayed no sign o e e sibili y o he second educ ion
p ocess a E
pa
(2) o high alues o (Fig. 5B and Fig. S13B†).
Spec oelec ochemical s udies pe o med wi h he Mo–N
2
complex 1also e ealed some diffe ences o i s W congene 2.
While oxida ion a E
pa
(1) led o disappea ance o he N
2
s e ching band a 1942 cm
−1
, no new IR-de ec able species
could be de ec ed in he 1800–2100 cm
−1
equency ange
(Fig. 5C). Mo eo e , upon back educ ion, he ini ial spec um
could only be pa ially eco e ed. In e es ingly, analysis a
lowe equencies (1400 o 1700 cm
−1
) displayed u he spec-
al changes upon elec ochemical oxida ion (Fig. 5D). Pushing
he po en ial un il E
pa
(2) induced e en la ge modi ica ion o
he spec a in his equency egion. Re u ning o he ini ial
po en ial alue pa ially es o ed he N
2
s e ching band a
1942 cm
−1
(Fig. 5D). No ably, he changes in he 1400 o
1700 cm
−1
equency ange we e no obse ed o he ungs en
complex upon oxida ion a E
pa
(2) (Fig. S13D†).
Al oge he , hese elec ochemical and spec oelec ochem-
ical in es iga ions essen ially e ealed wo esul s. Fi s , hey
Scheme 3 P oposed mechanism o he oxida ion p ocesses o he
ungs en (A) and molybdenum (B) pen aPod N
2
complexes.
Fig. 5 CVs (E/V s. Fc
+
/Fc) a a P wo king elec ode (diam. 1 mm) o [Mo(N
2
)(P
Me2
PP
Ph2
)] (0.4 mM) in THF/NaBPh
4
0.02 M (A) a = 0.02 V s
−1
and
(B) o = 0.02 V s
−1
(black), 0.05 V s
−1
( ed), 0.1 V s
−1
(g een), 0.2 V s
−1
(blue), 0.5 V s
−1
(cyan), 1 V s
−1
(pink) and 2 V s
−1
(oli e); he numbe s (1), (2),
(3) and (4) on he g aphics a e ela ed o he edox sys ems, see de ails in ex . (C) In a ed spec a o [Mo(N
2
)(P
Me2
PP
Ph2
)] (15 mM) in THF/NaBPh
4
20 mM eco ded du ing in si u spec oelec ochemical measu emen s be o e (black) and a e oxida ion a E
pa
(1) ( ed), hen e u ning back o he
ini ial po en ial (blue); (D) he same as (C) excep ha oxida ion a E
pa
(1) ( ed) is ollowed by oxida ion a E
pa
(3) (g een), E
pa
(2) (blue), hen e u ning
back o he E
pa
(1) (cyan) and finally he ini ial po en ial (magen a).
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36

3.1 Tungs en and molybdenum dini ogen complexes suppo ed by a pen aden a e e apodal
phosphine ligand: compa a i e spec oscopic, elec ochemical and eac i i y s udies
clea ly show ha one-elec on oxida ion o he neu al W and
Mo dini ogen complexes occu s a almos he same E
1/2
(1)
alue (−1.16 V and −1.13 V s. Fc
+
/Fc, espec i ely). This esul
is easonable on he basis o expe imen al da a ob ained om
NMR and IR spec oscopies as well as X- ay diff ac ion
( ide in a), which ha e shown mino diffe ences be ween he
wo neu al Mo and W complexes in solu ion and in he solid
s a e. I is also in line wi h elec ochemical in es iga ions
epo ed on Mo and W bis-N
2
complexes suppo ed by
P
Ph
N
Me
P
Ph
ligands, exhibi ing a diffe ence o only 20 mV o
he i s oxida ion po en ial.
24
Hence, ou esul s sugges ha
he s uc u al p ope ies o he W and Mo mono-oxidized dini-
ogen species a e e y simila .
The second in o ma ion which can be aken om elec o-
chemis y and spec oelec ochemis y is ha , al hough
W
I
(N
2
)
+
and Mo
I
(N
2
)
+
pen aPod complexes can be educed a
simila po en ial alues, hey display e y diffe en s abili ies
in THF (c . Scheme 3): whe eas he mono-oxidized ungs en N
2
species seems o be highly s able, yielding back he neu al N
2
complex upon educ ion, spec oelec ochemis y sugges s ha
i s Mo analogue e ol es apidly (sec) owa ds a new Mo
I
species, p obably a Mo
I
( h )
+
complex. Likewise, he W
II
(N
2
)
2+
species appea s a he second oxida ion p ocess as ai ly
uns able (msec) and may exchange i s N
2
ligand by a THF
ligand. Upon back educ ion, N
2
e-binds o he me al cen e
since he N
2
s e ching band is de ec ed. In he case o he
molybdenum complex, oxida ion beyond E
pa
(1) leads o a mo e
complica ed si ua ion and p obably induces N
2
–THF ligand
exchange. The anodic peak a E
pa
(3) may be hus asc ibed o
he oxida ion o Mo
I
( h )
+
species.
A las , compa ison wi h edox da a epo ed o o he dini-
ogen Mo and W complexes offe s in e es ing in o ma ion (see
Table 2). In pa icula , oxida ion po en ials o mononuclea
ans-bis-N
2
W and Mo complexes a e clea ly mo e posi i e
han hose o W and Mo pen aPod complexes by 150–370 mV,
likely esul ing om eplacemen o one dini ogen ligand by a
P-dono . In some cases, such as o ans-[Mo(N
2
)
2
(dppe)
2
], he
CV e e sibili y o he i s oxida ion was ound o be depen-
den on he expe imen al condi ions. Whe eas Cha e al.
desc ibed a e e sible sys em in THF/NBu
4
BF
4
o he i s oxi-
da ion p ocess,
26
Elson epo ed an i e e sible anodic peak a
oom empe a u e when using a THF/MeOH (26% / ) mix u e
wi h LiCl o LiClO
4
as suppo ing elec oly e.
23
In he la e
case, a ans-[Mo
I
(dppe)
2
(MeOH)
2
]
+
species was cha ac e ized
esul ing om he elease o N
2
acco ding o a dissocia i e
pa hway. On he o he hand, o ans-[Mo(N
2
)
2
(depe)
2
],
25
longe imescale yielded NuN bond clea age and Mo
IV
ni ide
o ma ion, diffe en ly o he complex 1.
Reac i i y o Mo and W complexes owa ds acids and SmI
2
/H
2
O
In case o he molybdenum pen aPod complex [Mo(N
2
)
(P
Me2
PP
Ph2
)] (1) he co esponding hyd azido(2-) complex
could be gene a ed by addi ion o B ookha ’s acid (HBA
F
,[H
(OE
2
)
2
][BA
F
], 2.5 equi .). No ably, his complex also exhibi ed
ca aly ic ac i i y owa ds ammonia gene a ion, indica ing ha
i is an in e media e o he ca aly ic cycle.
16
T ea men o he
ungs en dini ogen complex 2wi h 3 equi . o HBA
F
was
simila ly ound o gene a e he co esponding hyd azido(2-)
complex 3-BA
F
(Scheme 4; o IR da a see ESI Fig. S15 and
Table S7†). Using smalle amoun s o acid did no lead o a
pu e p oduc .
The
31
P NMR spec um o 3-BA
F
exhibi s an AA′MXX′
pa e n (Fig. 6, see Fig. S16–S26† o ull NMR da a), demon-
s a ing e en ion o he pen aphosphine en i onmen (a
signal a abou 0 ppm shows a small impu i y which mos
likely is caused by p o ona ion o he ligand, also iny amoun s
o ee ligand can be obse ed in he enla gemen in Fig. 7).
Howe e , all signals o 3-BA
F
ha e unde gone a high ield
shi compa ed o 2(Fig. 7), indica ing an inc eased shielding
o he P-dono s in he o me complex which is a ibu ed o
an elonga ion o he me al–P bonds and a loss o σ-dona ion
o he me al cen e. The pa icula ly la ge high- ield shi o
he M-signal upon p o ona ion o he N
2
-complex is due o he
la ge ans-in luence o he π-dona ing hyd azido(2-) ligand,
weakening he W–P
ax
bond. This analysis is suppo ed by DFT
calcula ions which show an inc ease o he W–P bond leng hs
upon going om 2 o 3-BA
F
, wi h a la ge elonga ion o he
Scheme 4 P o ona ion o [W(N
2
)(P
Me2
PP
Ph2
)] (2) o [W(NNH
2
)
(P
Me2
PP
Ph2
)]X
2
(X = BA
F
, Al(p b)
4
)(3).
Table 2 Elec ochemical da a o [LM
I/0
] dini ogen species
Complex E
1/2
/V s. Fc
+
/Fc Condi ions Re .
[W(N
2
)(P
Me2
PP
Ph2
)] (2)−1.16 THF/NaBPh
4
This wo k
[Mo(N
2
)(P
Me2
PP
Ph2
)] (1)−1.13 THF/NaBPh
4
This wo k
ans-[Mo(N
2
)
2
(depe)
2
]−1.01 THF/Py
4
FAP 25
−0.99
a
THF/NBu
4
BF
4
26
ans-[W(N
2
)
2
(dppe)
2
]−0.82 THF/NBu
4
[B(C
6
F
5
)
4
]24
ans-[W(N
2
)
2
(dppe)(dppp)] −0.79 THF/NBu
4
[B(C
6
F
5
)
4
]24
a
Expe imen ally measu ed a E
1/2
=−0.43 V s. SCE.
Dal on T ansac ions Pape
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37
Chap e 3 P ojec 1
W–P
ax
bond leng h in compa ison o W–P
eq
(Table S6†).
No ably, p o ona ion o 2wi h [H(OE
2
)
2
][Al(OC(CF
3
)
3
)
4
] (HAl
(p b)
4
) led o simila esul s (c . Fig. S27†).
The
31
P–
31
P coupling cons an s o he hyd azido(2-) complex
3-BA
F
show some diffe ences compa ed o he pa en dini o-
gen complex 2(Table 1). While he cis couplings among he
equa o ial phosphines a e almos unchanged (ΔJ=1–2Hz), he
co esponding ans coupling ge s smalle by abou 30 Hz. On
he o he hand, he cis couplings o he equa o ial phosphines
wi h he axial P dono a e inc eased by 17 and 13 Hz, espec -
i ely. Simila p o ona ion-induced changes ha e been obse ed
in he co esponding molybdenum sys em (Table 1).
15,16
Compa ison o he hyd azido(2-) complexes o ungs en and
molybdenum show simila diffe ences as o he dini ogen
complexes, excep ha he changes in he cis coupling con-
s an s be ween he equa o ial phosphines and he axial
P-dono a e smalle han o he co esponding dini ogen
complexes (Table 1). The
1
H–
15
N,
15
N–
15
N and
15
N–
31
P coup-
ling cons an s show nea ly iden ical, he co esponding alues
o he ungs en complexes always being sligh ly smalle
han o hei molybdenum coun e pa s (see Table S8 in
ESI†). Ne e heless, he
1
H–
15
N coupling cons an o 3-BA
F
(92.0 Hz) is s ill la ge han o a W-hyd azido(2-) complex
suppo ed by wo biden a e ligands (80 Hz).
27
Analogous o he
dini ogen complexes, DFT calcula ions indica e ha he bond
leng hs and bond angles o he molybdenum and ungs en
hyd azido(2-) complexes a e e y simila (Table S6†).
Mo eo e , he calcula ed N–N bond leng hs (∼1.31 Å) co es-
pond o hose ob ained o classic Cha - ype hyd azido(2-)
complexes.
28
In o de o in es iga e a po en ial ca aly ic ac i i y o he new
ungs en complex, a 0.1 M solu ion o sama ium diiodide and
wa e (5 ml) was ea ed wi h a THF solu ion o 2(2 µmol in
1 ml THF) unde ni ogen in a 50 mL Schlenk lask a oom
empe a u e. A e he solu ion u ned yellow he amoun o
p oduced ammonia was de e mined by he indophenol
me hod.
29
In con as o i s molybdenum congene 1,complex
2jus gene a ed a sligh ly o e -s oichiome ic amoun o
ammonia (2.75 ± 0.23 eq., 5% yield ela ed o he educing)
agen . Whe eas ammonia could be s oichiome ically p oduced
by p o ona ion o [W(N
2
)
2
(PMePh
2
)
4
],
11
a lack o (chemo)ca a-
ly ic NH
3
o ma ion om N
2
is well known o ungs en sys ems
(see abo e).
13,14
Thus, 2is he i s W complex ha is able o
gene a e mo e han 2 equi alen s o NH
3
in ela ion o he
me al cen e upon addi ion o p o ons and educ an . Howe e ,
i appea s ha jus a small ac ion o he dini ogen complex is
egene a ed, sugges ing ha mos o he ca alys is con e ed o
adiffe en complex ha is inac i e owa ds ni ogen educ ion.
In his con ex we no e ha addi ion o wa e o he ungs en
dini ogen complex wi hou sama ium diiodide esul ed in he
decomposi ion o he complex.
Summa y and conclusions
The ungs en dini ogen complex [W(N
2
)(P
Me2
PP
Ph2
)] (2)sup-
po ed by a pen aden a e e apodal phosphine ligand
(P
Me2
PP
Ph2
) has been syn hesized and cha ac e ized ega ding
i s elec onic s uc u e and eac i i y, allowing compa ison wi h
he analogous molybdenum complex [Mo(N
2
)(P
Me2
PP
Ph2
)] (1).
Reac ion o [W(N
2
)(P
Me2
PP
Ph2
)] (2) wi h sama ium iodide/wa e
was ound o media e a sligh ly o e s oichiome ic o ma ion
(2.75 ± 0.23 eq.) o NH
3
om N
2
which makes 2 he i s ung-
s en complex gene a ing mo e han 2 equi alen s o ammonia
om N
2
. No ably, he analogous molybdenum complex 1ca aly-
ically gene a es 25.7 eq. NH
3
om N
2
.
16
This con as ing beha -
iou o ungs en s. analogous molybdenum complexes ega d-
ing he ca aly ic con e sion o N
2
o NH
3
is well known in he
li e a u e,
8,13
bu no ully unde s ood. Wi h a ν
NN
alue o 1901
(2) s. 1929 cm
−1
(1) he ac i a ion o he N
2
ligand is highe in
he W complex han in i s Mo analogue, which he e o e canno
be he eason o he diffe ing beha iou . Apa om ha ,
howe e , diffe ences in s uc u al pa ame e s a e small.
Co espondingly, a single-c ys al s uc u e de e mina ion
Fig. 6 Expe imen al and simula ed
31
P{
1
H} NMR spec a o
15
N
2
-3-BA
F
(a) and 3-BA
F
(b). (c) O e all spec um o 3-BA
F
in die hyle he -d
10
.
Fig. 7 Compa ison o he
31
P{
1
H} NMR spec a o 2(black) and 3-BA
F
( ed).
Pape Dal on T ansac ions
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38
3.1 Tungs en and molybdenum dini ogen complexes suppo ed by a pen aden a e e apodal
phosphine ligand: compa a i e spec oscopic, elec ochemical and eac i i y s udies
o 2only showed mino diffe ences o bond dis ances and
angles wi h espec o 1. Likewise, he
31
P- and
15
N-NMR-spec-
oscopic p ope ies o 2we e ound o be qui e simila o hose
o 1, apa om cha ac e is ic diffe ences in chemical shi s and
coupling cons an s. Based on he s ong ac i a ion o N
2
,2
could be con e ed o he hyd azido(2-) de i a i e 3by p o ona-
ion wi h HBA
F
, simila o 1, ende ing compa ison o he ana-
logous Mo–NNH
2
complex possible as well.
In o de o ob ain in o ma ion abou he elec onic–s uc-
u al p ope ies o he ungs en and molybdenum pen aPod
sys ems, elec o- and spec oelec ochemical in es iga ions
we e pe o med on 1and 2. Bo h dini ogen complexes exhibi
ema kably simila edox po en ials. Mo eo e , wo main
sys ems can be de ec ed in oxida ion. Fo ungs en, he i s
sys em is ound o be e e sible and he second, being i e e s-
ible a low scan a es, ge s mo e e e sible a highe scan a es.
By con as , he i s sys em is only pa ially e e sible o he
molybdenum complex and i e e sible o he second sys em.
The o igin o hese diffe ences could be elucida ed wi h spec-
oelec ochemis y: upon oxida ion o 2, a s able W
I
N
2+
complex is o med whe eas o he molybdenum complex 1
loss o N
2
occu s, p obably going along wi h a ligand exchange
and o ma ion o a THF-bound complex. Fo W, loss o N
2
only
occu s upon u he oxida ion o he W
I
N
2+
complex.
In conclusion, he spec oelec ochemical s udies as well as
he ol amme ic s udies showed ha bo h sys ems can egen-
e a e he ze o alen dini ogen complexes a ound he same
po en ial. Fu he mo e, a s able ungs en dini ogen complex
is al eady o med a he le el o a W(I) in e media e, exhibi ing
a ai ly ac i a ed N
2
ligand wi h a ν
NN
o 1951 cm
−1
in solu ion.
By con as , he co esponding Mo(I) dini ogen complex is
he mally uns able. A heo e ical mechanism e alua ed o N
2
-
educ ion o he molybdenum pen aPod sys em indica ed ha
PCET o he Mo(N
2
)-complex, gene a ing a diazenido(-) in e -
media e, is ene ge ically mo e a ou able o a Mo(I)- han o
a Mo(0)-species.
16
Based on he esul s p esen ed he e, he
ungs en complex 2would i much be e o such a scena io
han i s molybdenum analogue 1. Ne e heless, NH
3
o -
ma ion media ed by 2is only sligh ly o e s oichiome ic. The
eason(s) o his obse a ion mus he e o e lie in some o he
s age o he ca aly ic cycle. Fu he in es iga ion o his ques-
ion is unde way.
Expe imen al sec ion
All syn heses we e pe o med unde N
2
o a gon a mosphe e
using s anda d Schlenk line and glo ebox echniques. The
sol en s we e d ied and eshly dis illed unde a gon p io o
use. [H(OE
2
)
2
][Al(OC(CF
3
)
3
)
4
] was ecei ed om he wo king
g oup o I. K ossing in F eibu g i. B .. All o he eagen s we e
comme cially a ailable and we e used as ecei ed.
[WCl
4
(PMePh
2
)
2
],
18
[Mo(N
2
)(P
Me2
PP
Ph2
)] (1)
15
and [Mo(NNH
2
)
(P
Me2
PP
Ph2
)]
16
we e p epa ed acco ding o he li e a u e. NMR
spec a we e eco ded wi h a B uke AVANCE III HD Pulse
Fou ie ans o m spec ome e ope a ing a equencies o
400.13 MHz (
1
H), 376.50 (
19
F), 161.98 MHz (
31
P), 128.38 (
11
B),
and 40.56 MHz (
15
N). Re e encing was pe o med ei he using
he sol en esidue signal (5.32 ppm o CD
2
Cl
2
, 3.58 ppm o
h -d
8
and 7.16 ppm o C
6
D
6
) o TMS (δ
1
H = 0 ppm), CFCl
3
(δ
19
F = 0 ppm), 85% H
3
PO
4
(δ
31
P = 0 ppm), BF
3
((δ
11
B=
0 ppm), and CH
3
NO
2
(δ
15
N = 0 ppm) se ing as subs i u i e
s anda ds. IR spec a we e eco ded a RT on a B uke Ve ex70
FT-IR spec ome e using a b oadband spec al ange ex en-
sion VERTEX FM o ull mid and a IR in he ange o
6.000–80 cm
−1
.
Elec ochemical s udies we e pe o med in a glo ebox
(Jacomex) (O
2
< 1 ppm, H
2
O < 1 ppm) wi h a home-made
3-elec ode cell (WE: P o glassy ca bon, RE: P wi e in a 1 mM
Fc
+
/Fc, 0.02 M THF/NaBPh
4
solu ion, CE: P ). Fe ocene was
added a he end o he expe imen s o de e mine he exac
edox po en ial alues. The po en ial o he cell was con olled
by an AUTOLAB PGSTAT 100 (Me ohm) po en ios a moni-
o ed by he NOVA© so wa e (Me ohm). The wo king elec o-
des we e polished o e a 1 μm alumina slu y wi h wa e , soni-
ca ed in H
2
O (18.2 Ωcm) and ace one, hen d ied wi h N
2
lush.
Thin laye IR spec oelec ochemis y was ca ied ou wi h a
p e iously desc ibed se -up consis ing o a comme cial IR Si
ATR p obe (A pho onics), which can i in o a hin space
c ea ed on he su ace o a glassy ca bon elec ode.
30
The hin
laye be ween he p obe and he elec ode allows as (seconds)
elec olysis, hence ime- esol ed moni o ing o he elec o-
chemical eac ion. De ec ion o he IR signal (2 cm
−1
esolu-
ion, one spec um e e y 10 s) was ob ained by using a FTIR
op ic- ibe -coupled spec ome e pu chased om A cop ix
(FTMIR-FC-120-LN2).
Single c ys al s uc u e de e mina ion
Da a collec ion was pe o med using an Imaging
Pla e Diff ac ion Sys em (IPDS-2) om S oe & Cie wi h Mo-Kα
adia ion. A nume ical abso p ion co ec ion was pe o med
using X-Red and X-Shape o he so wa e package X-A ea. The
s uc u es we e sol ed wi h SHELXT
31
and s uc u e e ine-
men was pe o med agains F
2
using SHELXL-2018
32
The C–H
hyd ogen a oms we e posi ioned wi h idealized geome y
(me hyl H a oms allowed o o a e bu no o ip) and we e
e ined iso opic wi h U
iso
(H) = 1.2U
eq
(C) (1.5 o me hyl H
a oms) using a iding model.
CCDC 2127859 (2) con ains he supplemen a y c ys allo-
g aphic da a o his pape .†
Compu a ional de ails
Calcula ions o he ungs en dini ogen [W(N
2
)(P
Me2
PP
Ph2
)] (2)
and hyd azido(2-) complexes [W(NNH
2
)(P
Me2
PP
Ph2
)]
2+
(3) we e
conduc ed wi h he ORCA 4.2.1 p og am package.
33
Geome ies we e op imized on PBE0
34
/de 2-TZVP
35
le el o
heo y. In addi ion, G imme’s dispe sion co ec ion wi h
Becke–Johnson damping (D3BJ)
36
and he RI app oxima ion
using he de 2-TZVP/J i ing basis se
37
we e used.
Dal on T ansac ions Pape
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39
Chap e 3 P ojec 1
[WCl
3
(κ
3
-P
Me2
PP
Ph2
)]
1.11 g (1.53 mmol) o [WCl
4
(PMePh
2
)
2
] and 1.24 g (1.83 mmol)
o P
Me2
PP
Ph2
we e dissol ed in 50 ml oluene and s i ed o
3 h a 70 °C. The mix u e was il a ed and concen a ed in
acuo o 5 ml and 10 ml o die hyl e he was added. The g een
p ecipi a e was il e ed and washed wi h 10 ml die hyl e he
and 10 ml n-pen ane. D ying in acuo ga e a da k g een solid.
Yield: 1.26 g (1.30 mmol, 85%). Anal. calcd o C
39
H
53
Cl
3
P
5
W:
C, 48.4; H, 5.52; ound: C, 48.9; H, 5.65. IR (300 K):
˜= 3067
(w), 3051 (w), 2954 (sh), 2919 (m), 2867 (sh), 2801 (w), 1589
(m), 1568 (w), 1551 ( w), 1480 (m), 1455 ( w), 1430 (m), 1412
(w), 1381 (w), 1330 ( w), 1297 (w), 1279 (w), 1260 ( w), 1241
(w), 1182 (w), 1156 (w), 1119 (w), 1096 (m), 1069 (w), 1025 (w),
1000 (w), 945 (m), 917 (m), 880 (m), 843 (w), 805 ( w), 739 (s),
693(s), 639 ( w), 617 (w), 577 ( w), 543 (w), 508 (s), 479 (m),
442 ( w), 425 (w), 404 ( w), 362 ( w), 340 (sh), 323 (sh), 294 (s),
271 ( s), 252 (sh), 221 ( w), 208 ( w), 178 (w), 158 (w), 133 (m),
120 (w) cm
−1
. Raman (300 K):
˜= 6054 (m), 2982 (w), 2913 (s),
1586 (s), 1455 ( w), 1414 (w), 1306 ( w), 1210 ( w), 1186 (w),
1160 (w), 1100 (w), 1073 ( w), 1028 (m), 1000 ( s), 960 (w), 786
(w), 688 (w), 619 (w), 400 ( w), 328 (w), 258 (w), 150 ( w) cm
−1
.
[W(N
2
)(P
Me2
PP
Ph2
)] (2)
290 mg (300 µmol) o [WCl
3
(κ
3
-P
Me2
PP
Ph2
)] we e dissol ed in
20 ml THF and added o sodium amalgam p epa ed o 2 ml
Hg and 200 mg (8.7 mmol) o sodium. The eac ion mix u e
was s i ed o 16 h unde an a mosphe e o ni ogen. The
supe na an ed solu ion was ans e ed in o ano he lask
and he sol en was emo ed in acuo. The esidue was
esol ed in 10 ml o die hyl e he and il e ed o e neu al
alumina. The o ange solu ion was concen a ed o d yness and
shed wi h small amoun s o cold n-pen ane o n-hexane.
D ying in acuo ga e an o ange solid. C ys als sui able o X- ay
single c ys al diff ac ion we e ob ained by slow diffusion o
n-pen ane in o a benzene-d
6
solu ion o 2. Yield: 118 mg
(133 µmol, 44%). Anal. calcd o C
39
H
53
N
2
P
5
W: C, 52.7; H,
6.01; N, 3.15. Found: C, 53.4; H, 6.04; N, 2.30. The ni ogen
alue is oo low because o he he mal ins abili y o he
p oduc .
1
H NMR (400.13 MHz, d
6
-benzene, 300 K): δ= 0.51 (d,
2
J= 5.2 Hz, 6H, PMe
2
), 0.81 (d,
2
J= 7.7 Hz, 2H, PCH
2
), 0.97 (m,
7H, Me
2
PCH
2
,CH
3
), 1.27 (m, 4H, PCH
2
), 1.93 (m, 4H,
CH
2
CH
2
CH
2
), 2.03 (m, 2H, Ph
2
PCH
2
), 2.43 (m, 2H, Ph
2
PCH
2
),
6.41 (m, 5H, PPh
2
), 6.75 (m, 2H, PPh
2
), 6.86 (m, 6H, PPh
2
), 7.09
(m, 4H, PPh
2
), 7.16 (m, 1H, PPh
2
), 7.28 (m, 2H, PPh
2
) ppm.
13
C
NMR (100.61 MHz, d
6
-benzene, 300 K): δ= 16.3 (m, 2C, PMe
2
),
23.9 (m, 4C, CH
2
CH
2
CH
2
), 26.2 (m, 2C, PMe
2
), 30.3 (s, 2C,
Ph
2
PCH
2
), 34.6 (m, 1C, PCH
2
), 38.6 (m, 2C, PCH
2
), 40.6 (s, 1C,
H
3
C), 42.0 (m, 1C, H
3
CC), 43.0 (m, 2C, Me
2
PC), 126.4 (s, 8C,
PPh
2
), 127.3 (d,
2
J= 7.4 Hz, 4C, PPh
2
), 127.8 (s, 2C, PPh
2
), 128.1
(m, 4C, PPh
2
), 129.1 (m, 2C, PPh
2
), 147.2 (m, 2C, PPh
2
), 150.0
(m, 2C, PPh
2
) ppm.
31
P{
1
H} NMR (161.98 MHz, d
6
-benzene,
300 K): δ=−4.8 (m,
2
J(P
AX′
,P
A′X
) = 85.7,
2
J(P
AM
,P
A′M
) = 11.2,
2
J
(P
AX
,P
A′X′
)=−11.1,
2
J(P
A
,P
A′
) = 17.4 Hz, 2P, PPh
2
,P
A
/P
A′
),
−21.3 ( ,
2
J(P
MX
,P
MX′
) = 18.5 Hz, 1P, P
M
), −35.8 (m,
2
J(P
X
,P
X′
)
= 4.5 Hz, 2P, PMe
2
,P
X
/P
X′
) ppm. IR (300 K):
˜= 3139 ( w), 3069
(w), 3049 (w), 2994 ( w), 2959 (m), 2920 (sh), 2906 (m), 2855
(m), 2812 (sh), 1982 (w), 1901 ( s, ν(N–N)), 1805 ( w), 1750
( w), 1585 (w), 1571 (w), 1481 (m), 1448 (w), 1431 (s), 1418 (sh),
1373 (w), 1328 ( w), 1293 (w), 1258 (s), 1218 ( w), 1184 ( w),
1153 (w), 1089 (s), 1072 (m), 1048 (m), 1025 (s), 970 (w), 925
(m), 905 (s), 875 (m), 832 (w), 798 (s), 737 (s), 693 ( s), 662 (s),
625 (s), 612 (s), 544 ( w), 506 ( s), 475 (m), 429 (w, ν(W–N)),
402 (s), 372 ( w), 345 (m), 313 (w), 290 (w), 263 ( w), 240 (m),
191 ( w) cm
−1
. Raman (300 K):
˜= 3053 (s), 2963 (w), 2912 ( s),
2888 (s), 2863 (sh), 1903 (s, ν(N–N)), 1587 (s), 1572 (w), 1451
( w), 1434 ( w), 1418 ( w), 1405 ( w), 1297 ( w), 1274 ( w), 1186
(w), 1156 (w), 1093 (m), 1029 (m), 1001 ( s), 933 ( w), 910 ( w),
670 (w), 637 ( w), 618 (w), 505 ( w), 431 (w, ν(W–N)), 403 ( w),
364 ( w), 350 ( w), 315 ( w), 292 ( w), 257 ( w), 242 (w), 193 (w)
cm
−1
.
15
N-[W(N
2
)(P
Me2
PP
Ph2
)] (
15
N-2) was p epa ed in a simila
ashion as 2unde a
15
N
2
a mosphe e and cha ac e ized by IR,
Raman,
31
P- and
15
N NMR spec oscopy.
15
N{
1
H} NMR
(40.56 MHz, d
10
-E
2
O, 300 K): δ=−18.7 (d,
1
J
NN
= 7.5 Hz, 1N,
N
β
), −48.4 (m, 1N, N
α
) ppm.
31
P{
1
H} NMR (161.98 MHz, d
6
-
benzene, H
3
PO
4
, 300 K): δ=−4.8 (m,
2
J(P
AA′
N
α
) = 2.7 Hz,
3
J
(P
AA′
N
β
) = 0.3 Hz, 2P, PPh
2
,P
A
/P
A′
), −21.3 ( dd,
2
J(P
M
,N
α
)=
13.9,
3
J(P
M
N
β
) = 1.6 Hz, 1P, P
M
), −35.8(m,
2
J(P
XX′
N
α
) = 2.6 Hz,
3
J(P
AA′
N
β
) = 0.7 Hz, 2P, PMe
2
,P
X
/P
X′
) ppm. IR (300 K):
˜= 1840
( s, ν(N–N)), 421 (w, ν(W–N)) cm
−1
. Raman (300 K):
˜= 1840 (s,
ν(N–N)), 419 (w, ν(W–N)) cm
−1
.
[W(NNH
2
)(P
Me2
PP
Ph2
)] (BA
F
)
2
(3-BA
F
)
A po ion o 99.0 mg (97.9 µmol) o [H(OE
2
)
2
][BA
F
] was dis-
sol ed in 0.4 mL o die hyl e he and added o 29 mg
(32.6 µmol) o 3 in 0.6 mL o die hyl e he . A e s i ing o
5 min a oom empe a u e he sol en was emo ed in acuo,
affo ding a ligh b own solid o nominal composi ion (de e -
mined by in eg a ion o he
1
H NMR signals) [W(NNH
2
)
(P
Me2
PP
Ph2
)](BA
F
)
2
·3HBA
F
. The high luo ine con en p e-
cluded an elemen al analysis.
1
H NMR (400.13 MHz, d
6
-
benzene, 300 K): δ= 0.85 (d,
2
J= 7.8 Hz, 6H, PMe
2
), 1.03 (m,
3H, CH
3
), 1.59 (d,
2
J= 9.7 Hz, 2H, PCH
2
), 1.73 (m, 8H,
Me
2
PCH
2
,PCH
2
), 2.24 (m, 4H, CH
2
CH
2
CH
2
), 2.66 (m, 2H,
Ph
2
PCH
2
), 2.98 (m, 2H, Ph
2
PCH
2
), 6.75 (m, 6H, PPh
2
), 6.90 (m,
2H, PPh
2
), 7.35 (m, 6H, PPh
2
), 7.42 (s, 22H, BA
F
), 7.62 (m,
38H, BA
F
), 7.68 (m, 4H, PPh
2
), 7.77 (m, 2H, PPh
2
) ppm.
13
C
NMR (100.61 MHz, d
6
-benzene, 300 K): δ= 16.7 (m, 2C, PMe
2
),
19.3 (s, 4C, CH
2
CH
2
CH
2
), 20.8 (m, 2C, PMe
2
), 26.0 (m, 2C,
PCH
2
), 28.5 (s, 2C, PCH
2
), 35.2 (m, 1C, PCH
2
), 35.4 (s, 1C,
H
3
CC), 36.0 (m, 2C, Me
2
PC), 116.0 (s, 4C, CH(BA
F
)), 123.4 (q,
1
J= 271.7 Hz, CF
3
), 127.4 (s, 8C, CH(BA
F
)), 128.0 (m, 8C,
CCF
3
), 128.0 (m, 8C, PPh
2
), 128.5 (s, 2C, PPh
2
), 129.6 (d,
2
J=
15.0 Hz, 4C, PPh
2
), 130.7 (m, 2C, PPh
2
), 131.4 (d,
2
J= 11.6 Hz,
4C, PPh
2
), 136.1 (d,
1
J= 44.1 Hz, 2C, PPh
2
), 136.1 (d,
1
J= 44.1 H
2C, PPh
2
), 137.0 136.1 (d,
1
J= 45.8 H 2C, PPh
2
), 160.2 (m, 4C,
BC) ppm.
11
B NMR (128.38 MHz, d
6
-benzene, 300 K): δ=−6.97
(s, 2B, BA
F
) ppm.
19
F NMR (376.50 MHz, d
6
-benzene, 300 K): δ
=−63.4 (s, 48F, BA
F
) ppm.
31
P{
1
H} NMR 161.98 MHz, d
10
-
E
2
O, 300 (K): δ=−15.9 (m,
2
J(P
AX′
,P
A′X
) = 53.9,
2
J(P
AM
,P
A′M
)=
28.2,
2
J(P
AX
,P
A′X′
)=−12.2,
2
J(P
A
,P
A′
) = 16.1 Hz, 2P, PPh
2
,P
A
/
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40
3.1 Tungs en and molybdenum dini ogen complexes suppo ed by a pen aden a e e apodal
phosphine ligand: compa a i e spec oscopic, elec ochemical and eac i i y s udies
P
A′
), −45.8 (m,
2
J(P
MX
,P
MX′
) = 31.3,
2
J(P
X
,P
X′
) = 6.3 Hz, 2P,
PMe
2
,P
X
/P
X′
), −48.6 ( , 1P, P
M
) ppm. IR (300 K):
˜= 3312 (w,
ν(N–H)), 3076 ( w), 2960 (w), 2924 (m), 2853 (w), 1790 ( w),
1611 (m), 1443 (w), 1352 (s), 1272 ( s), 1159 (m), 1114 ( s),
1092 (sh), 998 (w), 934 (w), 918 ( w), 886 (s), 838 (s), 809 (m),
743 (m), 711 (s). 698 (w), 680 (s), 669 (s), 617 ( w), 609 ( w),
580 (w), 568 ( w), 516 (w), 507 (w), 488 (w), 449 (m), 403 (w),
392 (w), 380 ( w), 366 (m), 353 (sh), 331 ( w), 283 (w), 259 (w),
246 ( w), 210 ( w), 189 ( w), 151 ( w) cm
−1
. Raman (300 K):
˜=
3074 (w), 3023 ( w), 2960 (8w), 2932 (m), 2906 (m), 2882 (sh),
2852 (w), 1611 (m), 1593 (s), 1523 ( w), 1464 (w), 1364 (s), 1107
(w), 1030 (w), 1003 ( s), 952 (w), 939 ( w), 914 ( w), 840 ( w),
801 (s), 745 (w), 704 (s), 689 (w), 675 (w), 617 ( w), 287 (w), 262
(w), 244 ( w), 235 (w), 183 (w), 159 (m) cm
−1
.
15
N-[W(NNH
2
)(P
Me2Ph2
)](BA
F
)
2
(
15
N-3-BA
F
) was p epa ed in
a simila ashion s a ing om
15
N-2 and cha ac e ized by IR,
Raman,
31
P- and
15
N NMR spec oscopy.
15
N{
1
H} NMR
(40.56 MHz, d
10
-E
2
O, 300 K): δ=−48.4 (m, 1N, N
α
), −237 (m,
1N, N
β
) ppm.
31
P{
1
H} NMR 161.98 MHz, d
10
-E
2
O, 300 (K): δ=
−15.9 (m,
2
J(P
AA′
N
α
) = 5.0 Hz, 2P, PPh
2
,P
A
/P
A′
), −45.8 (m,
2
J
(P
XX′
N
α
) = 5.5 Hz, 2P, PMe
2
,P
X
/P
X′
), −48.6 ( dd,
2
J(P
M
,N
α
)=
20.4 Hz,
3
J(P
M
N
β
) = 6.6 Hz, 1P, PM) ppm. IR (300 K):
˜= 3308
(w, ν(N–H)), 554 (w, ν(W–N)) cm
−1
.
[W(NNH
2
)(P
Me2
PP
Ph2
)][Al(p b)
4
]
2
(3-Al(p b)
4
) was p epa ed
simila o 3-BA
F
wi h [H(OE
2
)
2
][Al(OC(CF
3
)
3
)
4
] as acid.
Conflic s o in e es
The au ho s decla e no con lic o in e es .
Acknowledgemen s
The au ho s g a e ully acknowledge he SEA-EU p og am sup-
po ed by Agence Na ionale de la eche che (ANR-19-
GURE-0001), PHC P ocope Campus F ance (46652ZL) and
P og amm des P ojek bezogenen Pe sonenaus auschs
F ank eich (PROCOPE) 2021–2023 (Deu sche Akademische
Aus auschdiens , P ojek -Kennziffe 57560918) o unding.
The au ho s hank P o . Ingo K ossing o p o iding us wi h
[H(OE
2
)
2
][Al(OC(CF
3
)
3
)
4
].
Re e ences
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12 P. Ga ido-Ba os, J. De osa, M. J. Chalkley and J. C. Pe e s,
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17 E. Ca mona, A. Galindo, M. L. Po eda and R. D. Roge s,
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18 Ino ganic syn heses, ed. F. Basolo and R. J. Angelici, Wiley,
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19 S. L. Apps, A. J. P. Whi e, P. W. Mille and N. J. Long,
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20 F. B. Ogil ie, J. M. Jenkins and J. G. Ve kade, J. Am. Chem.
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22 J.-M. Sa éan , Elemen s o Molecula and Biomolecula
Elec ochemis y: An Elec ochemical App oach o Elec on
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23 C. M. Elson, Ino g. Chim. Ac a, 1976, 18, 209.
24 C. J. Weiss, A. N. G o es, M. T. Mock, W. G. Doughe y,
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Dal on T ansac ions Pape
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41

Chap e 3 P ojec 1
26 J. Cha , H. Wasi , G. J. Leigh, H. Neukomm, C. J. Picke
and D. A. Rankin, J. Chem. Soc., Chem. Commun., 1980, 1024.
27 C. J. Weiss, J. D. Egbe , S. Chen, M. L. Helm, R. M. Bullock
and M. T. Mock, O ganome allics, 2014, 33, 2189.
28 K. H. Ho n, N. Bö es, N. Lehne , K. Me smann, C. Nä he ,
G. Pe e s and F. Tuczek, Ino g. Chem., 2005, 44, 3016.
29 (a) M. W. Wea he bu n, Anal. Chem., 1967, 39, 971;
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30 C. Ga cia Bellido, L. Ál a ez-Miguel, D. Miguel, N. Lalaoui,
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31 G. M. Sheld ick, Ac a C ys allog ., Sec . A: Found. Ad ., 2015,
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32 G. M. Sheld ick, Ac a C ys allog ., Sec . C: S uc . Chem.,
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33 F. Neese, Wiley In e discip. Re .: Compu . Mol. Sci., 2018, 8,33.
34 J. P. Pe dew, K. Bu ke and M. E nze ho , Phys. Re . Le .,
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Pape Dal on T ansac ions
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42
3.2 Elec ochemical and Elec oca aly ic S udies
3.2 Elec ochemical and Elec oca aly ic S udies
In o de o in es iga e he dini ogen complexes, which a e e y sensi i e o ai and mois u e,
he elec ochemical measu emen s need o be pe o med unde an ine a mosphe e. Besides
cyclic ol amme y and coulome y, in es iga ions ega ding he elec oca aly ic ac i i y o
he complexes a e in he scope o he p esen hesis. Since a he ime, u iliza ion o he
glo e box was no ye an op ion, app op ia e essels o he desi ed applica ions had o be
de eloped. The equi emen s o measu emen s and ca aly ic s udies a e di e en , ye he
cells should be simila . Glass essels o elec ochemis y we e al eady a ailable, which lea es
he equi emen o an ai igh lid. Fo his, a lid composed o wo elemen s was designed.
The lowe pa (Figu e 3.1 black) ea u es a g oo e which i s a glass lip o he essels i s.
The cell is sealed by a second elemen made om PTFE wi h a g oo e ha holds an O- ing
o assu e an ai igh i . The wo pa s o he lid a e locked and held oge he by ou sc ews.
I is e y impo an ha he sc ews a e no igh ened oo much as he PTFE o he lid could
c ack upon oo much s ess. The PTFE lid o he cell has mul iple holes, which p o ide he
possibili y o di e en connec ions. Each hole pe ec ly i s a small ubbe sep um wi h a
igh i . In he in ended uses, he ubbe sep a se e as inse ion poin s o quasi- e e ence,
auxilia y elec odes and o he addi ion o p epa a ions, e.g. by a sy inge pump.
Fig. 3.1:
Ine gas cell designed o elec ochemical analy ics and use in elec oca aly ical expe imen s
In he cen e o he uppe lid is a hole ha is la ge han he o he ones. This cen al hole
can be used in wo ways. Fo elec ochemical measu emen s such as c , a wo king elec ode
can be inse ed which howe e equi es an addi ional i ing. By cu ing o he op o a small
ubbe sep um and ixing i o he elec ode wi h pa a ilm allows o an ai igh i . Using
his me hod cyclic ol amme y measu emen s unde ine condi ions we e achie ed. The gas
igh ness o he cell was de e mined by means o gas ch oma og aphy. The capabili y o he
43
Chap e 3 P ojec 1
sys em was es ed by measu ing he [W(N2)(P2MePP2Ph)] complex (Figu e 3.3).
Fig. 3.2:
The cyclic ol ammog ams o he [
W(N2)
(P
2Me
PP
2Ph
)] complex (c = 0.06 mmol/L) measu ed
wi h he cells build o he elec ochemical in es iga ions ( h , 0.1 mol/L TBAPF
6
). Display
is he o e iew ol ammog am (le ) and a measu emen o he edox e en s o he complex
( igh ). Two edox sys ems a e associa ed wi h he complex. The i s e e sible edox sys em
can be assigned o he oxida ion/ educ ion o W
0⇄
W
I
and he second, quasi- e e sible
sys em o he WI⇄WII.
The cyclic ol ammog ams ob ained o his complex and i s molybdenum analogue a e
iden ical o he ones ob ained in coope a ion wi h Le Poul om he Uni e si é de B e agne
Occiden ale B es . This demons a es he unc ionali y o he sys em. The cyclic ol ammo-
g ams shown in Figu e 3.3 a e e e enced o he po en ials known om he measu emen s
in B es . The main issue a he ime was ha he complexes we e measu ed agains a
quasi- e e ence elec ode and no e ocene/ e ocenium was added o compensa e o he
shi o he Ag-quasi- e e ence. None heless, he c s demons a e he unc ionali y o he cell
design.
The second applica ion o he cell is mean o elec oca aly ic in es iga ions. By inse ing
a glass ube, con aining a G4 i a he bo om, in o he la ge cen al hole, he wo king
elec ode is sepa a ed om he auxilia y elec ode allowing o elec olysis expe imen s. The
cen al hole is i ed wi h an addi ional o- ing inside a g oo e in he middle o he PTFE
lid, sealing he cell. Due o he in e ac ion o he o- ings be ween he wo pa s o he lid
and in he cen e hole wi h he sol en used, he cell is sealed e en be e . The polyme o
he o- ings akes up some o he sol en apo , leading o an inc ease in hei olume. As
o he cyclic ol amme y con igu a ion, he ai high ness o he cell in elec oca aly ic
con igu a ion was e i ied by GC measu emen s o he cell a mosphe e a e di e en ime
pe iods and a e expe imen s. Nei he wa e no oxygen could no be de ec ed in any o he
pe o med measu emen s.
44
3.2 Elec ochemical and Elec oca aly ic S udies
Fig. 3.3:
Se up o in es iga ions owa ds elec oca aly ic ac i i y o he complex using a me cu y
pool elec ode.
In o de o pe o m in es iga ions ega ding he elec oca aly ic ac i i y o he complexes,
a me cu y pool elec ode was used. This ype o elec odes has wo main ad an ages. The
i s ad an age is he big su ace o he elec ode, elimina ing any di usion limi a ions, ilm
o ma ion o deposi ion on he su ace by u iliza ion o a s i ing ba . The second ad an age
is he o e po en ial o he me cu y elec ode. As p o ons a e equi ed o ammonia gene a ion,
applica ion o low po en ials would lead o he hyd ogen e olu ion eac ion (HER) a he
elec odes su ace as he dominan eac ion, e en be o e ammonia would be gene a ed. Me cu y
has a e y high o e po en ial, allowing ela i ely low po en ials o be applied wi hou hyd ogen
e olu ion. I is impo an o no e ha he essel used o a me cu y pool ca hode di e s om
he ones used o measu emen s in he way ha he connec o o he wo king elec ode is
loca ed on he bo om o he essel.
The main disad an age o he cell shown in Figu e 3.1 is he olume equi ed o measu emen s.
Due o ha eason an iden ical lid sys em o essels wi h a smalle olume was build. One o
he essels was modi ied o elec oca aly ic s udies by inse ing a hick pla inum wi e in o
he bo om o glass.
45
Chap e 4 P ojec 2
PN3P pince and a ipodal iphos ligand ia appended 4-
e hinylphenyl uni s o TATA ( iaza iangulenium) pla o ms.
The esul ing unc ionalized ica bonyl complexes we e depos-
i ed on gold and s udied wi h a ange o su ace-spec oscopic
me hods.[10,22] As al e na i e headg oups o su ace s udies,
molybdenum dini ogen (o ca bonyl) complexes suppo ed by
linea PNP ligands may be en isioned.[25] No ably, in oducing
an e hinyl g oup in 4-posi ion o he cen al phenyl ing o he
PNPhP ligand (c . Scheme 1, bo om igh ) would enable simila
coupling s a egies o pla o ms o o ganic su ace laye s as
applied ea lie o PN3P and iphos ligands and de i ed
complexes (see abo e).[10,22]
The molybdenum ica bonyl complex [Mo(CO)3(PNPhPPh)]
suppo ed by he PNPhPPh ligand (Scheme 1, lowe igh ) has
been p epa ed by Keskin e al. and in es iga ed ega ding o
his s uc u al and spec oscopic p ope ies.[26] Va ious elec onic
ac o s we e explo ed o explain he p e e ed o ma ion o he
ac isome .[26] In o de o inc ease he ac i a ion o small
molecules such as CO o N2in molybdenum complexes
suppo ed by he PNPhPPh ligand,[25] i s e minal phenyl g oups
ha e o be eplaced by mo e elec on-dona ing alkyl esidues.
Co espondingly we syn hesized a se ies o linea PNPhPRligands
wi h di e en alkyl esidues R=Me, E , Pln, Cyp, iP , Cy, Bu and
s udied he s uc u al and elec onic p ope ies o de i ed
molybdenum ica bonyl complexes, using X- ay s uc u e
analysis and spec oscopy. As expec ed, all new complexes
exhibi a shi o he CO-s e ching equencies o lowe
wa enumbe s wi h espec o he pa en complex. Su p isingly,
howe e , all o hese complexes a e ound in he ac geome y,
ega dless o he s e ic demand o he alkyl subs i uen s. This is
in s ong con as o analogous complexes suppo ed by PNHP
ligands, whe e bo h, me and ac isome s can be iden i ied. In
an e o o unde s and his esul (and p o ide a gumen s
going beyond hose ad anced by Keskin e al. o accoun o
he ac cons i u ion o he pa en [Mo(CO)3(PNPhPPh)] complex;
see abo e), hypo he ical me - ac isome iza ion p ocesses a e
modeled by DFT o bo h PNPhP and PNHP complexes. These
calcula ions indica e ha me - ac isome iza ion is kine ically
hinde ed in Mo- ica bonyl complexes suppo ed by PNPhP
ligands whe eas i is he mally allowed in he analogous PNHP
sys ems.
Resul s and Discussion
Syn hesis and X- ay S uc u e De e mina ion
Mos o he PNP ligands (1a–1 and 1h) we e p epa ed by
eac ion o N,N-bis(2-chlo oe hyl)aniline wi h a seconda y
phosphine in he p esence o n-bu ylli hium (Scheme 2). Fo he
PNPhPiP ligand ( e minal isop opyl g oups, phenyl subs i uen
on he cen al ni ogen; 1 ), which was p e iously epo ed by
Cu ley e al.,[19,27] N,N-bis(2- osyle hyl)aniline ins ead o he
chlo ina ed analog was employed. The la e ou e was also
used by Kos as o he syn hesis o PNPhPPh (1a).[6]
All ligands could be ob ained in pu e o m and we e eac ed
wi h he p ecu so [Mo(CO)3(ch )] in oluene (ch =cyclohep a-
iene), leading o [Mo(CO)3(PNPhPR)] complexes wi h R=Ph
(2a), E (2c), Cyp (2e), iP (2 ), and Cy (2 g; c . Scheme 3 and
expe imen al sec ion, gene al p ocedu es A and B). As expec ed,
he solid ica bonyl complexes showed su icien ai -s abili y
o cha ac e iza ion ia in a ed spec oscopy. No ably, no all
a ge compounds could be p epa ed in his ashion. Speci i-
cally, he Mo ica bonyl complexes suppo ed by he ligands
PNPhPMe (2b), PNPhPln (2d) and PNPhP Bu (2h) could nei he be
isola ed in pu e o m no cha ac e ized in solu ion. Fo 2b and
2h, p oduc s we e ob ained which we e insoluble. IR in es-
iga ions indica e ha mos likely mix u es o di e en com-
plexes a e o med. On he o he hand, DFT calcula ions sugges
ha he complex 2h con aining e -bu yl g oups may no o m
due o s e ic easons (Table S2, Table S3, Figu e S63). In
pa icula , longe bond leng hs a e ound in he calcula ed
s uc u e o ac-[Mo(CO)3(PNPhP Bu)] (2h) as compa ed o [Mo-
(CO)3(PNPhPiP )] (2 ), which migh impede a comple e coo dina-
ion o he ligand. Fac o s in luencing he ela i e s abili ies o
he a ge complexes in solu ion will be analyzed la e in his
s udy, employing DFT calcula ions (see below).
Fo complex [Mo(CO)3(PNPhPE )] (2c), a single-c ys al X- ay
s uc u e de e mina ion could be pe o med, showing a acial
coo dina ion mode o he PNP ligand (Figu e 1, Table 1). This is
analogous o he ela ed complex ac-[Mo(CO)3(PNPhPPh)] (2a)
epo ed by Keskin e al.[26]
The bigges s uc u al di e ence be ween he wo ac-
[Mo(CO)3(PNP)] complexes 2a and 2 c is exhibi ed by he MoN
bond leng h which is 0.0703 Å sho e in 2 c han in 2a. On he
Scheme 2. Syn hesis scheme o he PNP ligands used in his s udy
(Pln=phospholano, PC4H8; Cyp=cyclopen yl).
Scheme 3. Syn hesis o [Mo(CO)3(PNPhPR)] complexes (PR=P).
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52

4.1 Molybdenum ica bonyl complexes suppo ed by linea PNP ligands: In luence o P- and
N-subs i uen s on s uc u e, s abili y and on he ac i a ion o small molecules
o he hand, he MoP dis ances a e inc eased in 2 c ela i e o
2a by 0.018 and 0.041 Å. This is due o he ac ha compa ed
o he diphenylphosphine g oups o 2a, he die hyl phosphine
g oups o 2c ha e a la ge sigma dono s eng h and a smalle
capaci y o π-backbonding. In e es ingly, he inc eased MoP
bond leng h ound in 2c appea s o en ail a sho e MoN
bond, sugges ing a le eling e ec o he cen al amine g oup
on he o e all binding p ope ies o he PNP ligand. This is also
e iden om he ac ha he MoC dis ances a e e y simila
in 2a and 2c. Ne e heless, ib a ional spec oscopy e eals
ha he CO ligands o 2c a e s onge ac i a ed han in 2a (c .
nex sec ion).
In a ed and Raman Spec oscopy
De ailed in o ma ion on he bonding and ac i a ion o CO
ligands is p o ided by IR and Raman spec oscopy. Mo eo e ,
he CO-s e ching ib a ions also e lec he me / ac isome ism
o he i le complexes. Fo an oc ahed al complex wi h acial
M(CO)3coo dina ion, g oup heo y p edic s wo bands in he
CO s e ching egion o he IR- and in he Raman-spec um (A1
and E). Due o he ac ual Cs-symme y o complexes 2 a,2c,2 e,
2 , and 2 g (Figu e 4 and Figu e S36, S44, S48, and S52), E spli s
in o A’’ and A’(2), in addi ion o A’(1) which co esponds o he
o ally symme ic, in-phase s e ching mode. In he Raman
spec um, he A’(1) band is ound o be e y weak o he acial
isome , while he A’’ and A’(2) bands a e s ong, clea ly isible in
case o 2c (Figu e 2). The me idional isome , on he o he hand,
would exhibi an in ense A’(1) band.[28] The e o e, ib a ional
spec oscopy shows ha ou [Mo(CO)3(PNPhPR)] complexes
always adop he acial coo dina ion mode in he solid s a e.
No ably, he in a ed and Raman spec a o he pa en
complex 2a eco ded by us di e om hose published by
Keskin e al.[26] While he A’(1) and A’’ ib a ions appea a
compa able equencies, he equency o he A’(2) mode gi en
by hese au ho s (1782–1796 cm1) is conside ably lowe han
obse ed by us (1808/1804 cm1; c . Table 2). Mo eo e , he
in ensi y o he A’(1) peak in he Raman spec um is ai ly high,
which would in p inciple speak agains he assignmen o a ac
geome y o 2a, as in e ed by hese au ho s on he basis o he
ib a ional spec a. We do no know he eason o his
disc epancy, bu no e ha ou IR- and Raman da a o 2a a e
consis en wi h hose ob ained o he o he complexes.
In e es ingly, o all in es iga ed complexes excep 2g, ou
ins ead o wo bands a e obse ed o he A’’ and A’(2) s e ching
ib a ions in he Raman spec a (Table 2). Complex 2c, in which
his spli ing is mos p onounced, shows a di e ence o Δν =12
and 10 cm1be ween he A’(2) and A’’ bands, espec i ely. This
spli ing is also obse ed when spec a o single c ys als o 2c
Figu e 1. Molecula s uc u e o ac-[Mo(CO)3(PNPhPE )] (2c). The hyd ogen
a oms ha e been omi ed o cla i y. The mal ellipsoids a e shown a 50%
p obabili y.
Table 1. MoX bond leng hs [Å] in complexes 2a and 2 c.
MoX bond[a] [Mo(CO)3(PNPhPE )][b]
(2c)
[Mo(CO)3(PNPhPPh)][c]
(2a)
Δ
MoN1 2.442 2.512 0.070
MoP1 2.514 2.496 0.018
MoP2 2.507 2.466 0.041
MoC41(ax) 1.938 1.933 0.005
MoC21(eq) 1.978 1.977 0.001
MoC31(eq) 1.973 1.979 0.006
[a] Numbe ing acco ding o Figu e 1; [b] his s udy; [c] Re . [26].
Figu e 2. IR and Raman spec um [cm1] o [Mo(CO)3(PNPhPE )] (2c). The CO
s e ching ib a ions a e assigned based on a Cssymme ic Mo(CO)3
agmen .
Table 2. Expe imen al Raman equencies [cm1] o he CO s e ching
ib a ions in [Mo(CO)3(PNPhPR)] complexes (R=Ph (2a), E (2c), Cyp (2 e), iP
(2 ), Cy (2g)).
Complex A’(1) A’’[a] A’(2)[a]
[Mo(CO)3(PNPhPPh)] (2a) 1921 1829/1819 1808/1804
[Mo(CO)3(PNPhPE )] (2c) 1906 1820/1810 1786/1774
[Mo(CO)3(PNPhPCyp)] (2e) 1907 1812/1795 1785
[Mo(CO)3(PNPhPiP )] (2g) 1901 1802/1794 1788/1780
[Mo(CO)3(PNPhPCy)] (2 ) 1906 1810 1791
[a] In case o spli ing bo h bands a e lis ed.
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53
Chap e 4 P ojec 2
we e measu ed, so i does no o igina e om impu i ies o a
mix u e o di e en compounds. In he c ys al s uc u es o 2c
and 2a, mo e han one molecule exis s wi hin he uni cell (Z=
8 and 4, espec i ely.)[26] In his case, he ib a ions o indi idual
molecules in he uni cell may couple ( o Z=2, e.g., in o in-
phase and ou -o -phase combina ions), and he co esponding
bands o peaks spli (Figu e 3). This e ec ( ac o g oup o
Da ydo spli ing) has al eady been obse ed o molybdenum
ca bonyl complexes.[29]
In addi ion o he coo dina ion mode, in o ma ion abou
he ac i a ion o he ca bonyl ligands can be de i ed om he
equencies o he s e ching ib a ions o he Mo(CO)3 ag-
men . This is in luenced by he σ-dona ion and π-accep ance
p ope ies o he phosphine and amine dono s. F om he
li e a u e, i is known ha he di e ence in σ-dona ion p ope -
ies o e ia y phosphines wi h di e en esidues is small.[30] In
con as , hei π-accep o p ope ies change signi ican ly, which
hen in luences he ib a ional equency o he CO in ans
posi ion. Co espondingly, o he complexes bea ing di e en
alkyl phosphines (2c,2e,2 , and 2 g) he obse ed A’(1) CO
s e ching equencies a e ai ly simila (Table 2), he bigges
di e ence (Δ(A’(1))=6 cm1) being ound be ween he sys ems
wi h PCyp2and PiP 2subs i uen s. In con as , he A’(1) equency
o complex 2a bea ing phenyl phosphines (1921 cm1) is
14 cm1highe han 2e, he alkyl phosphine complex wi h he
highes equency. This con o ms o a yl phosphines being
mo e π-backbonding han hei alkyl coun e pa s. O e all, he
ac i a ion o he CO ligands as a unc ion o he subs i uen s on
he phosphines is ound o inc ease in he ollowing sequence:
PPh2<PE 2�PCyp2�PCy2<PiP 2
NMR Spec oscopy
31P and 13C NMR spec oscopy in solu ion p o ides in o ma ion
on he me - ac isome ism o complexes 2 a,2c &2e–2g in
solu ion ia he 31P esonances o he P-dono s and he 13C
a oms o he ca bonyl ligands coupling wi h he phosphines,
espec i ely. Impo an ly, he low- ield shi s obse ed o he
31P-signals o he complexes (ca. 15–22 ppm) a e cha ac e is ic
o a acial binding geome y. In me idional complexes, la ge
low- ield shi s o he phosphine signals a e obse ed.[31] Whe e-
as he ac ion o ac complexes exceeds 99%, aces o me
isome s can also be de ec ed (<1%; c . Figu e 4 and Table S1).
O he byp oduc s appea o be e aca bonyl complexes which
esul om decomposi ion o hei ica bonyl analogs, as
epo ed in he li e a u e.[26] Comple e NMR da a a e gi en in
he Suppo ing In o ma ion.
Complemen a y in o ma ion can be de i ed om he 13C-
NMR spec a. Due o he low na u al abundance o his ca bon
iso ope (<1.1%), molecules con aining mo e han one 13C
nucleus can be neglec ed.[32] No ably, a 13C nucleus nex o a 31P
a om leads o di e en chemical en i onmen s o o he wise
equi alen 31P nuclei. Co espondingly, he coo dina ion mode
can be de i ed om he signal pa e ns eme ging in he 13C
NMR spec um by coupling o he 31P nuclei wi h he 13C a oms
s a is ically ound on he di e en ca bon posi ions. Speci ically,
ame idional coo dina ion geome y is e lec ed by wo iple s,
one o he CO ans o he amine g oup and one o he CO
ligands ans o each o he . In con as , a acial geome y gi es
ise o a iple o he axial ca bonyl ca bon ( esul ing om he
equal cis couplings o he equa o ial phosphines) and, o he
equa o ial ca bon a oms, o he X pa o an ABX spin sys em
wi h A and B ep esen ed by wo equa o ial 31P a oms (A=PA,
B=PBand X=13C; see Figu e 3 o complex 2c as an
example).[22,28]
In ag eemen wi h he esul s om 31P-NMR spec oscopy
(see abo e), he acial isome s a e ound wi h a ios o mo e
han 99% o all complexes (2 a,2c &2 e–2g). Fo hese species,
he X pa o he ABX spec um (see abo e) co esponds o a
six-line signal (see Figu e 5, op, “b” and bo om scheme). The
dis ance be ween lines 2 and 5 is equal o jJAX +JBX j, while he
sepa a ion be ween lines 1 and 6 (lines 3 and 4) equals 2jD++
D-j(2jD+-D-j, espec i ely). D+and D-a e de ined by
Equa ion (1). Fu he mo e, he ela i e in ensi ies o he inne
Figu e 3. Spli ing o he ca bonyl s e ches o [Mo(CO)3(PNPhPR)] (R=Cy (2g),
Ph (2a), E (2c)).
Figu e 4. 31P NMR spec um o he ac-[Mo(CO)3(PNPhPE )] complex (2 c)
including aces o he me idional isome a 48.9 ppm.
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54
4.1 Molybdenum ica bonyl complexes suppo ed by linea PNP ligands: In luence o P- and
N-subs i uen s on s uc u e, s abili y and on he ac i a ion o small molecules
and ou e lines wi h espec o lines 2 and 5 co espond o ɛ
and 1 - ɛ, espec i ely (c . Figu e 5, bo om), wi h he la e
gi en by Equa ion (2):[28,33]
D� ¼ 1
2 i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i
nAnB
ð Þ �0:5 JAX JBX
ð Þ½ �2þJ2
AB
q(1)
1e¼
1
4JAX JBX
ð Þ2
1
4JAXJBX
ð Þ2þJ2
AB
(2)
Based on hese equa ions, app oxima e alues o he
coupling cons an s JAX, JBX and JAB as well as he chemical shi
di e ence νA–νBwe e de e mined and subsequen ly e ined by
i ing o he expe imen al spec a (see Figu es S62-S65). The
shi s and coupling pa ame e s ound o he ca bonyl and
phosphine g oups o complexes 2a,2 c,2e, and 2 a e
collec ed in Table 3. In addi ion o simila chemical shi s o he
CO ligands, he coupling cons an s o he P-nuclei a e also e y
simila , indica ing no only simila geome ies bu also com-
pa able elec onic s uc u es. Un o una ely, complex 2g
showed such a weak solubili y in mos NMR sol en s ha i was
impossible o ob ain spec a o su icien quali y o de i e hese
pa ame e s.
Besides he ABX pa e ns o he equa o ial CO ligands, he
13C NMR signals o he e hylene b idges (Figu e 5c and 5d) and
e minal e hyl g oups (Figu e 5e and 5 ) also e lec coupling o
he phospho us a oms. Wi h dec easing spin-spin coupling o
he 13C and 31P nuclei, he di e ence be ween D+and D-
dec eases, leading o a smalle dis ance be ween he inne lines
(3 & 4). Mo eo e , he in ensi y o he ou e lines (1 & 6)
dec eases, which in u n inc eases he in ensi y o he inne
lines. This is, e.g., isible o he signal o he e hyl b idge
p oximal o he phospho us a om (Figu e 5d). Ul ima ely, he
six-line pa e n collapses in o a iple (Figu e 5c; a ows
indica e he posi ions o he e y weak ou e lines). Simila
spec a a e also obse ed o he o he complexes (Figu e S35,
S43, S47, S51, and S53). The de i ed 13C NMR pa ame e s a e
collec ed in Table 3.
The modynamics o Me al o PNP-Ligand Bonding
Da a ob ained om NMR, IR, and Raman spec oscopy indica e
a acial geome y o complexes 2a,2c,2e,2 , and 2 g in
solu ion and in he solid s a e. The me idional isome s a e only
isible as mino aces (<1%) (Figu e 4) in he 31P NMR spec a.
In o de o unde s and he p e e ence o he ligands o acial
coo dina ion, a DFT s udy was conduc ed. To his end ligand
exchange eac ions wi h he di e en ligands we e ea ed
heo e ically, conside ing bo h me and ac con igu a ions o
he en i e se ies o complexes. This allows o di ec ly compa e
hei ela i e s abili ies (Figu e 6, Table S8 & S9), leading o he
ollowing conclusions: (i) in ag eemen wi h he esul s o
Keskin e al., he acial isome o [Mo(CO)3(PNPhPPh] (2a) is mo e
a o able han i s me coun e pa ; (ii) a he modynamically
mo e s able ica bonyl complex (2c) is gene a ed by he
PNPhPE ligand whe eby he ac isome is also a lowe ene gy
han i s me analogue; (iii) o all PNPhPRligands wi h e minal
alkyl subs i uen s exhibi ing a highe s e ic demand han e hyl,
he s abili y o he de i ed Mo(CO)3complex dec eases and me
is a lowe ene gy han ac (Figu e 6).
No ably, bo h isome s o 2h wi h di- e -bu ylphosphine
g oups a e e y un a o able. In he acial isome , he bond
leng hs a e oo elonga ed o conside i a possible p oduc ;
acco dingly, he calcula ed ene gy is e y high. The me idional
geome y o 2h is mo e a o able, bu s ill a high ene gy
compa ed o all o he complexes (c . θO(P Bu3)=167.1°).[34] This
Figu e 5. Top: 13C NMR spec um o [Mo(CO)3(PNPhPE )] (2c) wi h he mul iple
ABX pa e ns o he di e en 13C a oms (a- ) ound due o he coupling o
he phospho us nuclei. The signals o NPh g oup a e ma ked wi h an as e isk
(*) and signals o sol en s wi h wo as e isks (**). A ows indica e ou e lines
o li le in ensi y. Bo om: Six-line pa e n eme ging om ABX-spec um.
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55
Chap e 4 P ojec 2
may explain he expe imen al inding his complex could no
be syn hesized (see abo e).
Al hough he calcula ions o e all sugges a p e e ence o
he me idional isome s o all Mo(CO)3complexes suppo ed by
PNPhPRligands wi h s e ically mo e demanding subs i uen s
han e hyl (c . Figu e 6), only he acial isome s we e ob ained
expe imen ally (see abo e). In o de o unde s and his
appa en con adic ion o he heo e ically calcula ed ene -
ge ics, we compa ed ou indings wi h esul s ob ained on
simila compounds in he li e a u e. No ably, Keskin e al. also
epo ed ha only acial [Mo(CO)3(PNPhPPh)] (2a) was ob ained
ini ially; he me idional isome only o med in a small amoun
when he acial complex was s o ed in solu ion o weeks.[26]
Howe e , [Mo(CO)3(PNHPR)] complexes wi h PNHPRligands (R=
iP , Cy, Bu) con aining a cen al NH dono ins ead o NPh seem
o beha e di e en ly.[35,36] Fo [Mo(CO)3(PNHPiP )]; e.g., a c ys al
s uc u e wi h acial geome y was ob ained,[35] bu he
co esponding NMR and IR spec a e lec a me idional
geome y (Supp. Ma . o e . [35]). Fu he mo e, [Mo-
(CO)3(PNHPCy)] is ound o exis in, bo h, me idional and acial
geome y in solu ion, wi h he a io o he wo isome s being
sol en -dependen .[36]
In o de o iden i y possible di e ences in he s abili ies o
PNPhP and PNHP complexes, analogous isodesmic calcula ions o
ligand exchange eac ions as pe o med o he o me (Fig-
u e 6) we e conduc ed o he la e sys ems as well (Figu e S59
& S60). In ag eemen wi h he PNPhP complexes, he ac isome s
end o become mo e un a o able wi h inc easing s e ic
demand o he phosphine esidues, accoun ing o he expe -
imen ally obse ed o ma ion o me isome s (along wi h hei
ac coun e pa s). The lack o obse a ion o me isome s in case
o he PNPhP complexes hus has o o be o kine ic, no
he modynamic o igin.
Theo e ical in o ma ion on possible me - ac isome isa ions
o [Mo(CO)3(PNP)] complexes in solu ion can be ob ained by
DFT calcula ions as well. In p inciple, hese p ocesses can occu
in a non-dissocia i e ashion ia dis o ed oc ahed al ansi ion
s a es (Figu e 7, Figu e S65 & S66). In e es ingly, calcula ions o
he co esponding ene gy ba ie s o model complexes wi h
PMe2g oups (PNHPMe), e eal ha he ansi ion s a es o he
amine PNHPMe and phenylamine PNPhPMe sys ems (Figu e 7,
TSISONRCO3) a e un a o able. The co esponding ene gy ba ie s o
a ound 30 kcal/mol make such ans o ma ions unlikely. Addi-
ionally, no clea di e ences be ween he NH and NPh ligands
we e ound, which con as s wi h he expe imen al obse a-
ions, showing signi ican ly di e en beha iou .
Ano he p ocess possibly enabling an isome ic ans o ma-
ion in ol es he p elimina y dissocia ion o a CO ligand om
he 18-elec on [Mo(CO)3(PNRP)] complexes, leading o pen a-
coo dina e squa e-py amidal 16-elec on complexes [Mo-
(CO)2(PNRP)] (Figu e 8 and 9, Figu e S67 & S68, Table S10).[26,37]
The esul ing emp y coo dina ion si e makes i ene ge ically
much mo e a o able o he ligand o unde go a con o ma-
ional ea angemen . No ably, his dissocia i e subs i u ion
mechanism has been expe imen ally e idenced o [Mo-
(CO)3(PNPhPPh)] (2a) by Keskin e al.[26]
Table 3. Chemical shi and coupling cons an s o he equa o ial ca bonyl ligands o he ac-[Mo(CO)3(PNPhPR)] complexes.
Complex δ(13COax)
[ppm]
δ(13COeq)
[ppm]
δ(31P)
[ppm] j2JAB j
[Hz]
2JAX ( ans)
[Hz]
2JBX (cis)
[Hz]
~νAB
[Hz]
[Mo(CO)3(PNPhPPh)] (2a) 231.6 219.6 38.0 21.6 39.4 14.0 1.30
[Mo(CO)3(PNPhPE )] (2c) 231.4 220.3 33.7 29.1 32.4 10.8 1.80
[Mo(CO)3(PNPhPCyp)] (2e) 232.0 220.8 41.6 22.7 36.5 13.7 0.97
[Mo(CO)3(PNPhPiP )] (2 ) 231.9 220.8 51.6 26.5 33.7 8.8 1.69
[Mo(CO)3(PNPhPCy)] (2g) 232.1 221.0 40.8 – – – –
Figu e 6. Theo e ical ela i e Gibbs ene gies (including sol a ion) o he
acial and me idional [Mo(CO)3(PNPhPR)] complexes wi h di e en phosphine
g oups (R=E (2c), Ph (2 a), Cyp (2 e), iP (2 ), Cy (2g), Bu (2h)), ela i e o
he mos s able complex me -2c and calcula ed by ligand exchange
eac ions (PBE0/de 2-TZVPP).
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56
4.1 Molybdenum ica bonyl complexes suppo ed by linea PNP ligands: In luence o P- and
N-subs i uen s on s uc u e, s abili y and on he ac i a ion o small molecules
The ene gies o he co esponding dissocia i e in e medi-
a es [Mo(CO)2(PNRPMe)] (R=H, Ph) indica e ha only he CO
ligands ans o P o CO coligands dissocia e, leading o squa e-
py amidal isome s wi h he amine dono in equa o ial posi ion
(Figu e 8 and 9, ac1NH, me 1NH, me 2NH, ac1NPh and me 2NPh).
The e o e, only hese a e aken in o accoun o he subsequen
ebinding o CO and indeed, a signi ican ly di e en beha io is
obse ed o he NH and NPh ligands p esen ed he e:
In he case o [Mo(CO)2(PNHPMe)], wo equally s able me
isome s a e ound (Figu e 8, me 1NH and me 2NH) which a e in
equilib ium wi h each o he ia a e y low-lying igonal
bipy amidal ansi ion s a e (Figu e 8, TSMERNHCO2). This makes
bo h isome s equally a ailable o con e sion in o a acial
isome . The ac ual isome ic ans o ma ion hen occu s be ween
me 1NH and ac1NH ia a dis o ed igonal bipy amidal ansi ion
s a e (TSISONHCO2). Due o he ela i ely low ene gy ba ie o
11 kcal/mol om me 1NH o 3 kcal/mol om ac1NH,me and ac
complexes a e in an equilib ium in solu ion, which is in
acco dance wi h he expe imen al obse a ions in he
li e a u e.[36]
In case o [Mo(CO)2(PNPhPMe)], only one me idional and one
acial isome is s able due o an agos ic hyd ogen bond
be ween he phenyl g oup and he molybdenum cen e , which
occupies he acan coo dina ion si e (me 1NPh and ac1NPh,
Figu e 9). This and he s e ic demand o he mig a ing NPh
g oup lead o a much highe ene gy ba ie o 18 kcal/mol om
me 1NPh o 9 kcal/mol om ac1NPh complexes, making his
p ocess ei he impossible o a leas e y slow. The e o e, he
ini ial geome y o he complex esul ing om eac ion o he
p ecu so wi h he PNP ligand is conse ed. Fo ac-[Mo-
Figu e 7. Theo e ical ela i e Gibbs ene gies in solu ion o he isome ic
ans o ma ion o ac- and me -[Mo(CO)3(PNRPMe)] model complexes (R=H
( ed), Ph (blue)) ia ansi ion s a e TSISONRCO3 (PBE0/de 2-TZVPP(D3BJ))
(P=PMe2)
Figu e 8. Theo e ical ela i e Gibbs ene gies in solu ion o he isome s o pen acoo dina ed model complex [Mo(CO)2(PNHPMe)], including he isome ic
ans o ma ion ia ansi ion s a e TSISOHand he con e sion o he wo possible me idional isome s ia TSme (PBE0/de 2-TZVPP(D3BJ)) (P=PMe2).
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57

Chap e 4 P ojec 2
(CO)3(ch )], which has been used in his s udy o complexa ion
o he PNPhPRligands, i has been es ablished ha eac ion wi h
linea iden a e ligands exclusi ely leads o ac-complexes.[38,39]
Due o he high ba ie s, con e sion o possibly lowe -lying
me -isome s hus is hinde ed, explaining he lack o obse a ion
o me -isome s.
Conclusions
In o de o s udy he in luence o he di e en phosphine
g oups on he coo dina ion beha io o PNP ligands and
examine hei impac on he ac i a ion small molecules like CO,
a se ies o iden a e PNPhPRligands (R=Ph, Me, E , Pln, Cyp, iP ,
Cy, Bu) and co esponding molybdenum ica bonyl complexes
[Mo(CO)3(PNPhPR)] (R=Ph, E , Cyp, iP , Cy,) we e p epa ed and
cha ac e ized by NMR and ib a ional spec oscopy. In case o
[Mo(CO)3(PNPhPE )] he de e mina ion o he c ys al s uc u e was
possible as well.
Upon eplacing he PNPhPPh ligand o he pa en complex
[Mo(CO)3(PNPhPPh)] by ligands wi h alkylphosphine g oups he
ac i a ion o he bound ca bonyl ligands was ound o inc ease.
Wi hin he se ies o new complexes suppo ed by PNPhPR
ligands wi h alkyl subs i uen s, howe e , di e ences in CO
s e ching equencies and, hus, CO ac i a ion, we e small.
Ne e heless, he ela i e s abili ies o hese complexes signi i-
can ly dec ease wi h inc easing s e ic bulk o he e minal alkyl
subs i uen s R. This becomes e iden om isodesmic calcula-
ions, eplacing, e.g., he PNPhPPh ligand o he pa en [Mo-
(CO)3(PNPhP)] complex by co esponding ligands wi h PR2
g oups (R=E , Cyp, iP , Cy). This way, i becomes clea ha he
he modynamically mos s able membe o he en i e amily o
PNPhPRcomplexes is [Mo(CO)3(PNPhPE )], exhibi ing s ongly
elec on-dona ing PE 2g oups wi h li le s e ic bulk. On he
o he hand, hese calcula ions p o ide an explana ion o he
ac ha he complex wi h he s e ically mos demanding e -
bu yl subs i uen s could no be ob ained.
Expe imen al and heo e ical in o ma ion was also ob ained
on he p e e ed s e eochemical con igu a ion (me s. ac) o
he [Mo(CO)3(PNPhPR)] complexes. Su p isingly, all o he syn he-
sized [Mo(CO)3(PNPhPR)] complexes exhibi he ac geome y,
i espec i e o he elec onic and s e ic p ope ies o he
e minal phosphine g oups. This is, e.g., e iden om NMR
spec oscopy whe e he me idional isome s we e only ound as
mino byp oduc s isible in small amoun s (<1%) in he 31P
spec a. Mo eo e , he p e e ed o ma ion o he ac isome s
could also be in e ed om X- ay s uc u e de e mina ion and
ib a ional spec oscopy whe e ypical CO spli ing pa e ns
we e obse ed. Addi ional spli ings p esen in he IR and
Raman spec a we e a ibu ed o ac o g oup o Da ydo
spli ings.
Fo he pa en [Mo(CO)3(PNPhPPh)] complex (2a) he p e e -
ence o he ac-isome had al eady been e idenced by Keskin
e al. No ably, hey we e able o gene a e he ac isome om
he complex [Mo(CO)4(k2-PNPhP)] wi h a yield o <1%. Fu he -
mo e, hey ound ha he me isome is o med in small
amoun s upon le ing a solu ion o he ac isome s and o a
long ime. F om hei obse a ions, hey concluded ha he
me -isome is o med om i s ac coun e pa by a ac!me
isome iza ion p ocess p oceeding ia a dissocia i e pa hway.
This scena io has also been ad anced by C ab ee ega ding he
s e eoisome ism o [Mo(CO)3L3] complexes.[37]
Theo e ical suppo o he hypo hesis ha he ac-isome
o he complex [Mo(CO)3(PNPhPPh)] is mo e s able han i s me
coun e pa was ob ained by Keskin e al. om DFT
calcula ions.[26] No ably, Siclo an e al. syn hesized he [M-
(CO)3(PNMeP)] (M=Mo, W) complex and also ound he acial
isome o be mo e s able han i s me idional analog.[7] In his
con ex i has o be no ed ha a gene al elec onic-s uc u al
p e e ence o he ac geome y in Mo(0) ica bonyl complexes
esul s om he ac ha all h ee 2g a e able o in e ac in an
equal ashion wi h he CO ligands in a π-backbonding manne
whe eas his is no possible o he me con igu a ion. Howe e ,
his elec onic e ec should po en ially be coun e ac ed by a
s e ic e ec i he esidues on he e minal phosphine dono s
become mo e bulky han phenyl g oups. Fo s e ically e y
demanding subs i uen s, his ul ima ely may lead o a p e e -
ence o he me con igu a ion. This is in ac obse ed o
molybdenum ica bonyl complexes suppo ed by PNHP
ligands,[35,36] bu appa en ly does no apply o ou sys ems.
In o de o add ess his p oblem, calcula ions o he ela i e
s abili ies o me - ac isome s ha e been pe o med o he
Figu e 9. Theo e ical ela i e Gibbs ene gies in solu ion o he di e en
isome s o pen acoo dina ed model complex [Mo(CO)2(PNPhPMe)], including
isome ic ans o ma ion ia ansi ion s a e (TSISOPh) (PBE0/de 2-TZVPP(D3BJ))
(P=PMe2).
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58
4.1 Molybdenum ica bonyl complexes suppo ed by linea PNP ligands: In luence o P- and
N-subs i uen s on s uc u e, s abili y and on he ac i a ion o small molecules
en i e se ies o complexes. While he he mal s abili y o hese
complexes o e all dec eases wi h inc easing s e ic bulk o he
subs i uen s (see abo e), hese calcula ions also e eal ha a
p e e ence o he ac isome is es ic ed o he PNPhPPh
complex and he PNPhPE complex which exhibi s he leas
s e ically demanding alkyl subs i uen s. Fo all complexes wi h
bulkie esidues he me isome s a e he modynamically
a o ed. Howe e , his is no obse ed expe imen ally. We hus
suspec ed ha o ma ion o he me p oduc s migh be
kine ically hinde ed in all o hese complexes.
In o de o check his hypo hesis, po en ial ac-me isome -
iza ion p ocesses ha e been ea ed wi h he help o DFT.
No ably, calcula ions o he model sys ems [Mo(CO)3(PNRPMe)]
(R=H, Ph) showed ha a di ec isome ic ans o ma ion o
hese hexacoo dina ed complexes is unlikely. Ne e heless, i
can occu a e p elimina y dissocia ion o CO, in he cou se o a
dissocia i e p ocess (see abo e). Ou calcula ions indica e ha
such a p ocess is he mally allowed in he PNHP sys ems, bu is
hinde ed in he PNPhP sys ems due o he s e ic demand o he
phenyl g oup and an agos ic in e ac ion p esen bo h in he
acial and he me idional isome s in ol ed in he ans o ma-
ion. This ac s o signi ican ly inc ease he ene ge ic ba ie o
isome iza ion in PNPhP sys ems, making i e y slow o e en
supp essing i comple ely. The s e eoisome ic con igu a ion o
he p ima y p oduc s esul ing om eac ion o he Mo(CO)3
p ecu so wi h he PNPhP ligands hus is mo e o less e ained.
As i has been es ablished ha eac ion o he p ecu so ac-
[Mo(CO)3(ch )] wi h linea iden a e ligands exclusi ely leads o
ac p oduc s,[38,39] i becomes unde s andable ha all o he
in es iga ed complexes 2a,2 c,2e,2 , and 2g exhibi he ac
geome y and no me isome s ha e been obse ed. This
s e eochemical peculia i y o he PNPhP ligands may en ail
cha ac e is ic di e ences in he eac i i y o de i ed ansi ion-
me al complexes o analogues suppo ed by PNHP ligands,
compa able o hose e idenced be o e in he con ex o CO2
hyd ogena ion ca alyzed by Ru(PNHP) and -PNPhP complexes.[19]
Expe imen al Sec ion
Ma e ials and me hods: All syn heses con aining ai - and mois u e-
sensi i e compounds we e ca ied ou unde a ni ogen a mos-
phe e using Schlenk echniques. All sol en s we e d ied unde
a gon a mosphe e p io o use. Comme cially a ailable subs ances
we e used as pu chased wi hou u he pu i ica ion. The chemicals
used o syn hesis we e ob ained om Sigma-Ald ich Co., abc
GmbH & Co. KG., and Fishe Scien i ic GmbH.
Spec oscopy: The NMR spec a we e measu ed on a B uke A ance
III HD 400 pulse Fou ie T ans o m spec ome e a 400.13 MHz (1H),
100.61 MHz (13C), and 161.98 MHz (31P). The spec a we e ei he
e e enced o sol en esidue (5.32 ppm o CD2Cl2) o TMS (δ1H=
0 ppm), 85% H3PO4(δ31P=0 ppm) as subs i u i e s anda ds. The IR
spec a we e measu ed on a B uke alpha FT-IR spec ome e and
he Raman spec a on B uke Ve ex70 FT-IR wi h RAMII module.
The elemen al analyses we e pe o med using a Va ioMICRO cube
elemen analyze .
Single C ys al S uc u e De e mina ion: Da a collec ion was
pe o med wi h an X aLAB Syne gy, Dual lex di ac ome e wi h a
mic o ocus ube using CuKα adia ion (λ=1.54184). The s uc u e
was sol ed wi h SHELXT[40] using In insic Phasing and e ined wi h
SHELXL[41] using Leas Squa es minimisa ion. All non-hyd ogen
a oms we e e ined aniso opically. The CH H a oms we e
posi ioned wi h idealized geome y (me hyl H a oms allowed o
o a e bu no o ip) and we e e ined iso opic wi h Uiso(H)=
1.2 Ueq(C) (1.5 o me hyl H a oms using a iding model. Deposi ion
Numbe 2156795 con ains he supplemen a y c ys allog aphic da a
o his pape . These da a a e p o ided ee o cha ge by he join
Camb idge C ys allog aphic Da a Cen e and Fachin o ma ionszen-
um Ka ls uhe Access S uc u es se ice.
Compu a ional de ails: All calcula ions we e pe o med using he
ORCA 4.2.1 p og am package[42] wi h PBE0 unc ional[43] and de 2-
TZVPP basis se .[44] Fu he mo e, G immes dispe sion co ec ion[45]
wi h Becke-Johnson damping (D3BJ),[46] densi y i ing app oxima-
ion (RIJCOSX)[47] and sol a ion co ec ion (CPCM) we e applied.[48]
All minimum s uc u es we e op imized o ha e no imagina y
equencies. The ansi ion s a es we e op imized wi h exac ly one
imagina y equency.
Gene al p ocedu es and syn hesis: The syn heses o dime hyl
phosphine,[49] diisop opyl phosphine,[50] phospolane,[51] NN-bis(2-
chlo oe hyl)aniline[52] and N,N-bis(2-(p-
oluenelsul onyl)e hyl)aniline[25] we e p epa ed acco ding o li e -
a u e.
Gene al p ocedu e A: Syn hesis o he PNP ligands. 1 eq. o NN-
bis(2-chlo oe hyl)aniline was dissol ed in h and cooled o 0°C. In
a second essel, he phosphine (2.1 eq.) was also dissol ed in THF,
cooled o 0°C and n-bu ylli hium solu ion (2.5 mol/L) was added
d opwise o e 20 min. The solu ion was s i ed o 30 min a 0°C.
Wi hin 15 min he NN-Bis(2,2-dichlo oe hyl)aniline solu ion was
added o he phosphine/n-bu ylli hium solu ion a 0°C. The
solu ion was s i ed o 18 h a oom empe a u e. 0.5 mL degassed
wa e was added and he sol en was e apo a ed in acuo. The
esidue was esol ed in n-pen ane (30 mL) and il e ed h ough
Celi e® and basic aluminum oxide.
Gene al p ocedu e B: Syn hesis o he molybdenum ica bonyl
complexes. 1 eq. o [Mo(CO)3(ch )] was dissol ed in 3 mL oluene
gi ing a ed solu ion. The PNP-Ligand was dissol ed in 2 mL
oluene and added o he p ecu so complex solu ion. The solu ion
was s i ed o 18 h in he glo ebox. The esul ing c ude p oduc
was il e ed and washed wi h n-pen ane (5 mL). The p oduc was
d ied in acuo esul ing in a yellowish solid.
NN-Bis(2-(diphenylphosphino)e hyl)aniline (PNPhPPh, 1 a)
Following gene al p ocedu e A, he PNPhPPh (1a) ligand was
ob ained as colou less solid (796 mg, 1.54 mmol, 67%).
31P{1H} NMR: (161.98 MHz, CD2Cl2, 300 K): δ=-20.1 (s, 2 P, PPh2)
ppm.
1H NMR (400.13 MHz, CD2Cl2, 300 K): δ=7.35–7.30 (m, 8 H, P-
(CH)phenyl), 7.26–7.22 (m, 12 H, P-(CH)phenyl), 7.03–6.99 (m, 2 H, N-
(CH)phenyl), 6.56–6.52 (m, 1 H, N-(CH)phenyl), 6.28–6.26 (m, 2 H, N-
(CH)phenyl), 3.29–3.24 (m, 4 H, N-CH2), 2.22–2.18 (m, 4 H, P-CH2) ppm.
13C{1H} NMR (100.62 MHz, CD2Cl2, 300 K): δ=145.7 (s, 1 C, N-
(Ci,phenyl)), 139.9 (d, JPC =12.2 Hz, 4 C, P-(Ci,phenyl)), 131.7 (d, JPC =
18.8 Hz 8 C, P-(Co,phenyl)), 128.2 (s, 2 C, N-(Co,phenyl)), 127.7 (s, 4 C, P-
(Cp,phenyl)), 127.4 (d, JPC =6.80 Hz 8 C, P-(Cm,phenyl)) 115.4 (s, 1 C,
Cp,phenyl), 111.2 (s, 2 C, Cm,phenyl), 46.6 (d, 2JPC =25.6 Hz, 2 C, N-CH2),
25.0 (d, JPC =14.4 Hz, 2 C, P-CH2) ppm.
IR (ATR): ~
=3068 (w), 3049 (w), 3025 (w), 3018 (sh), 3001 (w), 2961
(w), 2928 (w), 2902 (w). 2869 (sh), 2855 (w), 1969 ( w), 1957
( w),1914 ( w), 1903 ( w), 1886 ( w), 1808 (w), 1764 ( w), 1595 (s),
Wiley VCH Mon ag, 28.08.2023
2399 / 317727 [S. 9/15] 1
Eu . J. Ino g. Chem. 2023, e202300280 (9 o 14) © 2023 The Au ho s. Eu opean Jou nal o Ino ganic Chemis y published by Wiley-VCH GmbH
Resea ch A icle
doi.o g/10.1002/ejic.202300280
10990682c, 0, Downloaded om h ps://chemis y-eu ope.onlinelib a y.wiley.com/doi/10.1002/ejic.202300280 by Coch ane Ge many, Wiley Online Lib a y on [18/09/2023]. See he Te ms and Condi ions (h ps://onlinelib a y.wiley.com/ e ms-and-condi ions) on Wiley Online Lib a y o ules o use; OA a icles a e go e ned by he applicable C ea i e Commons License
59
Chap e 4 P ojec 2
1571 (m), 1501 (s), 1476 (s), 1461 (w), 1429 (s), 1414 (w), 1389 (m),
1359 (w), 1352 (m), 1337 (w), 1319 ( w), 1305 (w), 1275 (sh), 1260
(s), 1218 (w), 1195 (s), 1180 (w), 1148 (m), 1094 (m), 1064 (w), 1039
(w), 1026 (w), 1011 (w), 995 (w), 984 (w), 947 (w), 913 (w), 907 ( w),
865 (m), 815 (sh), 794 (s), 734 ( s), 688 ( s), 667 (sh), 614 ( w), 554
(m), 528 (m), 504 ( s), 476 ( s), 430 (m), 411 (sh) cm1.
NN-Bis(2-(dime hylphosphino)e hyl)aniline (PNPhPMe, 1 b)
Following gene al p ocedu e A, he PNPhPMe (1b) ligand was
syn hesized, howe e , he phosphine solu ion was cooled o 78°C
ins ead o 0°C as desc ibed in he p ocedu e. The ligand (1 b) was
ob ained as colou less oil (236.7 mg, 0.88 mmol, 63%).
31P{1H} NMR: (161.98 MHz, CD2Cl2, 300 K): δ=-54.9 (s, 2 P, PMe2)
ppm.
1H NMR (400.13 MHz, CD2Cl2, 300 K): δ=7.22–7.17 (m, 2 H, CHphenyl),
6.68–6.61 (m, 3 H, CHphenyl), 3.45–3.39 (m, 4 H, CH2), 1.70–1.65 (m, 4
H, CH2), 1.06 (d, 2JPH =2.29 Hz, 12 H, CHme hyl) ppm.
13C{1H} NMR (100.62 MHz, CD2Cl2, 300 K): δ=147.4 (s, 1 C, Ci,phenyl),
129.2 (s, 2 C, Co,phenyl), 115.7 (s, 1 C, Cp,phenyl), 112.2 (s, 2 C, Cm,phenyl),
47.7 (d, 2JPC =21.4 Hz, 2 C, N-CH2), 29.8 (d, 1JPC =12.6 Hz, 2 C, P-CH2),
13.8 (d, JPC =13.1 Hz, 4 C, P-CH3) ppm.
IR (ATR): ~
=3090 (w), 3058 (w), 3038 (w), 3023 (w), 2951 (s), 2923
(m), 2892 (s), 2853 (sh), 2812 (w), 1598 (s), 1574 (sh), 1504 (s), 1461
( w), 1449 ( w), 1428 (sh), 1420 (m), 1394 (w), 1354 (s), 1292 (sh),
1278 (m), 1213 (w), 1186 (m), 1159 ( w), 1142 (sh), 1128 (m), 1084
( w), 1042 (m), 1007 (b m), 990 (w), 967 ( w), 938 (s), 885 (m), 818
(w), 747 (s), 710 (w), 694 (s), 668 (w), 531 ( w), 508 (w), 434 ( w),
416 ( w) cm-1.
NN-Bis(2-(die hylphosphino)e hyl)aniline (PNPhPE , 1 c)
Following gene al p ocedu e A, he PNPhPE (1c) ligand was
ob ained as colou less oil (411 mg, 1.26 mmol, 25%).
31P{1H} NMR: (161.98 MHz, CD2Cl2, 300 K): δ=-25.7 (s, 2 P, PE 2) ppm.
1H NMR (400.13 MHz, CD2Cl2, 300 K): δ=7.20–7.16 (m, 2 H, CHphenyl),
6.67–6.60 (m, 3 H, CHphenyl), 3.45–3.40 (m, 4 H, N-CH2), 1.70–1.65 (m,
4 H, P-CH2), 1.48–1.42 (m, 8 H, P-CH2-CH3), 1.11–1.03 (m, 12 H, P-
CH2-CH3) ppm.
13C{1H} NMR (100.62 MHz, CD2Cl2, 300 K): δ=147.4 (s, 1 C, Ci,phenyl),
129.3 (s, 2 C, Co,phenyl), 115.8 (s, 1 C, Cp,phenyl), 112.3 (s, 2 C, Cm,phenyl),
48.3 (d, 2JPC =22.6 Hz, 2 C, N-CH2), 24.3 (d, 1JPC =15.9 Hz, 2 C, P-CH2)
19.0 (d, 1JPC =18.9 Hz, 4 C, P-CH2-Me), 13.8 (d, 2JPC =12.6 Hz, 4 C,
-CH3) ppm.
IR (ATR): ~
=3085 (w), 3043 (w, b ), 2955 (w), 2923 (s), 2877 (s), 2821
(sh), 2821 (sh), 2220 (w), 2135 (w), 1600 (s), 1505 (s), 1436 (s), 1400
(m), 1368 (s), 1210 (w), 1200 ( w) 1158 (s), 1131 (s), 989 (m), 967
( w), 842 (sh), 789 (sh), 747 ( s), 695 (s), 619 ( w), 567 (w), 513 (w),
451 ( w) cm-1.
NN-Bis(2-phospholanoe hyl)aniline (PNPhPln, 1 d)
NN-Bis(2-chlo oe hyl)aniline (320 mg, 147 mmol) was dissol ed in
THF (10 mL). In a second essel li hium phospholanide (500 mg,
2.95 mmol) was dissol ed in 8 mL THF and cooled o 0°C. 1.2 mL
(3.00 mmol) o n-bu ylli hium solu ion was added d opwise and
s i ed in he cold o 40 min. The aniline solu ion was added slowly
o he phosphine/n-buli solu ion and i was s i ed o 4 d a oom
empe a u e. All ola ile componen s we e emo ed in acuo and
he esidue was ex ac ed wi h n-pen ane and dichlo ome hane
be o e il e ing h ough celi e and basic allox. The sol en s we e
emo ed yielding a yellow oil as p oduc (233 mg, 0.72 mmol,
49%).
31P{1H} NMR: (161.98 MHz, CDCl3, 300 K): δ=-32.0 (s, 2 P, Pln) ppm.
1H NMR (400.13 MHz, CDCl3, 300 K): δ=7.24–7.20 (m, 2 H, CHphenyl),
6.68–6.64 (m, 3 H, CHphenyl), 3.41–3.36 (m, 4 H, N-CH2), 1.85–1.65 (m,
4 H, P-CH2, 8 H, (CH2)Pln), 1.63–1.59 (m, 4 H, (CH2)Pln), 1.53–1.46 (m, 4
H, (CH2)Pln), ppm.
13C{1H} NMR (100.62 MHz, CDCl3, 300 K): δ=146.1 (s, 1 C, Ci,phenyl),
128.3 (s, 2 C, Co,phenyl), 114.9 (s, 1 C, Cp,phenyl), 111.2 (s, 2 C, Cm,phenyl),
47.7 (d, 2JPC =21.4 Hz, 2 C, N-CH2), 26.8 (d, 1JPC =3.8 Hz, 4 C, (CH2)Pln),
25.8 (d, JPC =18.6 Hz, 4 C, P-CH2), 25.0 (d, 1JPC =11.0 Hz, 4 C, (CH2)Pln)
ppm.
IR (ATR): ~
=3090 (w), 3057 (w), 3038 (w), 3023 (w), 2929 (s), 2873
( w), 2855 (s), 2823 (sh), 2675 ( w), 1916 (w), 1905 (w), 1600 ( s),
1570 (sh), 1502 ( s), 1457 (w), 1445 (m), 1352 (s), 1322 (sh), 1298
( w), 1275 (sh), 1256 (s), 1209 ( w), 1183 (m), 1157 ( w), 1118 (sh),
1107 (s), 1087 (sh), 1054 ( w), 1039 (w), 1013 (s), 950 ( w), To2 ( w),
859 (w), 828 (sh), 792 (s), 743 ( s), 688 ( s), 657 ( w), 620 ( w), 561
( w), 508 (m), 466 ( w), 398 (m) cm1.
NN-Bis(2-(dicyclopen ylphosphino)e hyl)aniline (PNPhPCyp, 1 e)
Following gene al p ocedu e A, he PNPhPCyp (1e) ligand was
ob ained wi h he excep ion ha he solu ion was s i ed o 4 d
yielding he p oduc as colou less solid (540 mg, 1.11 mmol, 76%).
31P{1H} NMR: (161.98 MHz, CDCl3, 300 K): δ=-7.93 (s, 2 P, PCp2)
ppm.
1H NMR (400.13 MHz, CDCl3, 300 K): δ=7.24–7.20 (m, 2 H, CHphenyl),
6.68–6.63 (m, 3 H, CHphenyl), 3.49–3.44 (m, 4 H, N-CH2), 1.97–1.85 (m,
8 H, CH2, Cp), 1.74 (m, 2JPH =2.35 Hz, 3JHH =8.79 Hz, 4 H, P-CH2), 1.70–
1.63 (m, 8 H, CH2, Cp), 1.62–1.51 (m, 8 H, CH2, Cp), 1.48–1.33 (m, 8 H,
CH2, Cp) ppm.
13C{1H} NMR (100.62 MHz, CDCl3, 300 K): δ=147.2 (s, 1 C, Ci,phenyl),
129.5 (s, 2 C, Co,phenyl), 115.8 (s, 1 C, Cp,phenyl), 112.2 (s, 2 C, Cm,phenyl),
49.2 (d, 2JPC =40.6 Hz, 2 C, N-CH2), 36.2 (d, 2JPC =10.3 Hz, 4 C, P-CCp)
31.3 (d, 1JPC =16.9 Hz, 4 C, P-CCp), 30.5 (d, 2JPC =12.5 Hz, 4 C, P-CCp),
26.6 (d, 3JPC =7.40 Hz, 4 C, P-CCp), 26.3 (d, 3JPC =6.30 Hz, 4 C, P-CCp),
22.8 (d, 1JPC =17.9 Hz, 2 C, P-CCp) ppm.
IR (ATR): ~
=3211(w, b ), 3089 (w), 3060 (w), 3036 (w), 3018 (w),
2942 ( s), 2902 (w), 2858 ( s), 2056 ( w), 1904 ( w), 1800 ( w), 1752
( w), 1602 (s), 1595 (s), 1566 (m), 1506 ( s), 1466 (sh), 1455 (sh),
1444 (s), 1402 (s), 1350 (s), 1320 ( w), 1283 (s), 1260 (w), 1215 (w),
1184 ( s), 1155 ( w), 1126 (s), 1086 (sh), 1059 ( w), 1034 (m), 1002
(s), 980 (w), 942 ( w), 921 ( w), 904 (m), 853 (m), 800 (m), 755 (sh),
738 ( s), 703 (sh), 689 ( s), 545 (m), 508 (s), 490 ( w), 457 ( w), 423
(w) cm1.
NN-Bis(2-(diisop opylphosphino)e hyl)aniline (PNPhPiP , 1 )
Diisop opylphosphine (0,67 g, 5.67 mmol) was sol ed in 10 mL THF
and cooled o 0°C. n-Bu ylli hium solu ion in hexane (2.4 mL,
6.00 mmol) was added d opwise and s i ed o 30 min a 0°C.
A e wa ds, he solu ion was s i ed o an addi ional 30 min a
oom empe a u e. The solu ion u ned o ange. NN-Bis(2-(p-
oluenelylsul onyl)e hyl)aniline (1.26 g, 2.57 mmol) was dissol ed in
10 mL THF and bo h solu ions we e cooled o 0°C. The phospine/n-
bu ylli hium solu ion was added d opwise o he aniline gi ing a
yellow solu ion. A e an hou , he solu ion u ned g een and ed/
o ange a e 18 h. The eac ion was quenched wi h degassed wa e
(5 mL) and all ola ile componen s we e emo ed in acuo. The
Wiley VCH Mon ag, 28.08.2023
2399 / 317727 [S. 10/15] 1
Eu . J. Ino g. Chem. 2023, e202300280 (10 o 14) © 2023 The Au ho s. Eu opean Jou nal o Ino ganic Chemis y published by Wiley-VCH GmbH
Resea ch A icle
doi.o g/10.1002/ejic.202300280
10990682c, 0, Downloaded om h ps://chemis y-eu ope.onlinelib a y.wiley.com/doi/10.1002/ejic.202300280 by Coch ane Ge many, Wiley Online Lib a y on [18/09/2023]. See he Te ms and Condi ions (h ps://onlinelib a y.wiley.com/ e ms-and-condi ions) on Wiley Online Lib a y o ules o use; OA a icles a e go e ned by he applicable C ea i e Commons License
60
4.1 Molybdenum ica bonyl complexes suppo ed by linea PNP ligands: In luence o P- and
N-subs i uen s on s uc u e, s abili y and on he ac i a ion o small molecules
esidue was esol ed in 40 mL die hyl e he and il e ed h ough
Celi e® and basic aluminium oxide. The PNPhPiP (1 ) ligand was
ob ained as colou less oil (411 mg, 1.26 mmol, 25%).
31P{1H} NMR: (161.98 MHz, CD2Cl2, 300 K): δ=1.53 (s, 2 P, PiP 2) ppm.
1H NMR (400.13 MHz, CD2Cl2, 300 K): δ=7.24–7.20 (m, 2 H, CHphenyl),
6.68–6.62 (m, 3 H, CHphenyl), 3.51–3.46 (m, 4 H, N-CH2), 1.79 (dsep .,
2JPH =2.11 Hz, 3JHH =7.11 Hz, 4 H, P-CH), 1.71–1.65 (m, 4 H, P-CH2),
1.15–1.08 (m, 24 H, P-CH-CH3) ppm.
13C{1H} NMR (100.62 MHz, CD2Cl2, 300 K): δ=147.2 (s, 1 C, Ci,phenyl),
129.3 (s, 2 C, Co,phenyl), 115.6 (s, 1 C, Cp,phenyl), 112.1 (s, 2 C, Cm,phenyl),
50.4 (d, 2JPC =32.2 Hz, 2 C, N-CH2), 23.4 (d, JPC =12.3 Hz, 4 C, P-CH)
20.0 (d, 2JPC =16.3 Hz, 4 C, P-CH-Me), 19.8 (d, JPC =12.6 Hz, 2 C,
CH2-P), 18.7 (d, 2JPC =9.40 Hz, 4 C, P-CH-Me) ppm.
IR (ATR): ~
=3091 (w), 3061 (w), 3038 (w), 2958 (sh), 2945 ( s), 2923
(w), 2887 (w), 2861 ( s), 1914 ( w), 1595 ( s), 1571 ( w), 1500 ( s),
1456 (s), 1382 (m), 1361 (sh), 1350 (s), 1277 (m), 1235 ( w), 1214 (w),
1183 (m), 1158 (w), 1127 (m), 1099 ( w), 1086 (sh), 1035 (s), 1014
(w), 993 (m), 919 (m), 887 (m), 859 (w), 806 (w), 742 ( s), 716 (w),
693 (s), 649 (w), 619 (w), 572 ( w), 509 (w), 466 (w) cm1.
NN-Bis(2-(dicyclohexylphosphino)e hyl)aniline (PNPhPCy, 1 g)
Following gene al p ocedu e A, he PNPhPCy (1 g) ligand was
ob ained as colou less solid (2.00 mg, 3.69 mmol, 99%).
31P{1H} NMR: (161.98 MHz, CD2Cl2, 300 K): δ=-8.21 (s, 2 P, PCy2)
ppm.
1H NMR (400.13 MHz, CD2Cl2, 300 K): δ=7.21–7.17 (m, 2 H, CHphenyl),
6.63–6.59 (m, 3 H, CHphenyl), 3.44–3.38 (m, 4 H, N-CH2), 1.79–1.63 (m,
24 H, CH2), 1.60–1.53 (m, 4 H, P-CH2), 1.32–1.14 (m, 20 H, CH2) ppm.
13C{1H} NMR (100.62 MHz, CD2Cl2, 300 K): δ=147.1 (s, 1 C, Ci,phenyl),
129.2 (s, 2 C, Co,phenyl), 115.4 (s, 1 C, Cp,phenyl), 112.1 (s, 2 C, Cm,phenyl),
50.4 (d, 2JPC =33.2 Hz, 2 C, N-CH2), 33.3 (d, JPC =12.7 Hz, 4 C, CH2),
30.4 (d, 2JPC =14.9 Hz, 4 C, CH2), 29.1 (d, JPC =7.93 Hz, 4 C, CH2), 27.3
(d, JPC =19.5 Hz, 4 C, CH2), 27.3 (s, 4 C, CH2), 26.6 (s, 4 C, CH2), 19.5
(d, JPC =20.3 Hz, 2 C, P-CH2) ppm.
IR (ATR): ~
=3087 ( w), 3058 (w), 3037 ( w), 3019 ( w), 2918 (s),
2894 (sh), 2846 (s), 2788 (sh), 2654 ( w), 2262 (w b ), 1603 (s), 1587
(s), 1570 (m), 1537 ( w), 1505 (s), 1461 (m), 1446 (s), 1397 (s), 1352
(s), 1268 (m), 1215 (m), 1201 (m), 1185 (s), 1178 (s), 1159 (m), 1128
(s), 1117 (sh), 1105 (m), 1089 (sh), 1072 (w), 1039 (m), 1018 (sh), 998
(s), 951 ( w), 931 (m), 921 (m), 887 (m), 851 (s), 818 (m), 807 (sh),
770 (sh), 758 (m), 739 (s), 707 (w), 687 (s), 549 (w), 507 (s), 458 (m),
439 (m), 402 (w) cm1.
NN-Bis(2-(di- e -bu ylphosphino)e hyl)aniline (PNPhP Bu, 1 h)
Following gene al p ocedu e A, he PNPhP Bu (1h) ligand was
ob ained as whi e solid (1.39 g, 3.18 mmol, 79%).
31P{1H} NMR: (161.98 MHz, CDCl3, 300 K): δ=25.0 (s, 2 P, P Bu2) ppm.
1H NMR (400.13 MHz, CDCl3, 300 K): δ=7.17–7.06 (m, 2 H, CHphenyl),
6.62–6.52 (m, 3 H, CHphenyl), 3.44–3.39 (m, 4 H, N-CH2), 1.64–1.58 (m,
4 H, P-CH), 1.71–1.65 (m, 4 H, P-CH2), 1.08 (d, 3JPH =11.3 Hz, 36 H,
CH3) ppm.
13C{1H} NMR (100.62 MHz, CDCl3, 300 K): δ=145.8 (s, 1 C, Ci,phenyl),
128.4 (s, 2 C, Co,phenyl), 114.6 (s, 1 C, Cp,phenyl), 110.7 (s, 2 C, Cm,phenyl),
50.6 (d, 2JPC =40.6 Hz, 2 C, N-CH2), 30.2 (d, 1JPC =19.4 Hz, 4 C, P-C)
28.6 (d, 2JPC =13.6 Hz, 12 C, CH3), 18.2 (d, JPC =22.7 Hz, 2 C, CH2-P)
ppm.
IR (ATR): ~
=3093 (w), 3063 (w), 3039 (w), 3025 (w), 2982 (sh), 2950
(sh), 2937 ( s), 2892 (m), 2860 (m), 2706 ( w), 1910 ( w), 1750 ( w),
1602 (s), 1590 (w), 1569 ( w), 1541 ( w), 1503 ( s), 1462 ( s), 1452
(sh), 1408 (sh), 1393 (w), 1383 (s), 1358 ( s), 1344 ( s), 1321 (sh),
1280 (s), 1203 (sh), 1183 ( s), 1123 ( s), 1081 ( w), 1036 (s), 1014
(m), 992 (m), 933 (sh), 922 (m), 854 (m), 810 (s), 768 (sh), 750 (sh),
742 ( s), 707 (m), 688 ( s), 618 ( w), 593 (m), 578 (m), 545 ( w), 535
( w), 506 (s), 464 (w), 434 (s) cm1.
[Mo(CO)3(PNPhPPh)] (2 a)
Following gene al p ocedu e B, he [Mo(CO)3(PNPhPPh)] (2a) was
ob ained as yellow solid (45.2 mg, 0.07 mmol, 34%). Pa s o he
analy ical da a was al eady p esen ed by Cowley e al.[26]
31P{1H} NMR: (161.98 MHz, CD2Cl2, 300 K): δ=38.0 (s, 2 P, PPh2)
ppm.
1H NMR (400.13 MHz, CD2Cl2, 300 K): δ=7.78–7.73 (m, 4 H, CHphenyl),
7.49–7.46 (m, 2 H, CHphenyl), 7.42–7.35 (m, 6 H, CHphenyl), 7.33–7.28 (m,
2 H, CHphenyl), 7.27–7.20 (m, 2 H, CHphenyl), 7.19–7.14 (m, 4 H, CHphenyl),
7.13–7.07 (m, 3 H, CHphenyl), 6.99–6.96 (m, 4 H, CHphenyl), 3.71–3.59 (m,
2 H, N-CH2), 3.21–3.08 (m, 2 H, N-CH2), 2.85–2.69 (m, 4 H, P-CH2)
ppm.
13C{1H} NMR (100.62 MHz, CD2Cl2, 300 K): δ=231.6 ( , 2JPC =8.24 Hz,
1 C, COaxial), 219.7 (ABX, 2 C, COequa o ial), 153.8 (s, 1 C, N-(Ci,phenyl)),
139.1–138.5 (m, 2 C, P-(Ci,phenyl)), 137.0–136.7 (m, 2 C, P-(Ci,phenyl)),
132.4 ( , JPC =6.13 Hz, 4 C, P-(Co,phenyl)), 131.2 ( , JPC =6.33 Hz, 4 C, P-
(Co,phenyl)), 130.0 (s, 2 C, P-(Cp,phenyl)), 129.4 (s, 2 C, P-(Cp,phenyl)), 129.1–
128.9 (m, 10 C, P-(Cm,phenyl), N-(Co,phenyl)), 125.3 (s, 1 C, N-(Cp,phenyl)),
121.1 (s, 2 C, P-(Cm,phenyl)), 58.0 ( , JPC =5.86 Hz, 2 C, N-(CH2)), 28.8 (dd,
JPC =9.51 Hz, JPC =6.67 Hz, 2 C, P-CH2) ppm.
IR (ATR): ~
=3837 ( w), 3717 ( w), 3616 ( w), 3599 ( w), 3548 ( w),
3078 ( w), 3055 (w), 3017 (w), 3002 ( w), 2977 ( w), 2927 ( w), 2895
(w), 2874 (w), 2849 (w), 1921 ( s, CO s e ch), 1802 (sh, b , CO
s e ch), 1775 (sh, CO s e ch), 1600 (m), 1586 (m), 1572 (m), 1494
(m), 1480 (m), 1432 (s), 1424 (sh), 1407 (w), 1377 ( w), 1331 (w),
1310 (sh), 1299 (w), 1223 (m), 1185 (m), 1095 (s), 1068 (m), 1037
(m), 1029 (m), 998 (sh), 991 (w), 971 ( w), 944 (w), 920 ( w), 905 (m),
898 (sh), 852 (sh), 843 (w), 813 (sh), 804 (s), 763 (m), 742 ( s), 695
( s), 671 (m), 651 (s), 634 (s), 610 (m), 597 (m), 554 (m), 530 (m), 515
( s), 499 ( s), 487 (sh), 467 (m), 459 (sh), 449 (w), 428 ( s) cm1.
Raman:~
=3069 ( w), 3143 ( w), 3081 (w), 3056 ( s), 3007 (b , w),
2989 ( w), 2979 ( w), 2957 (w), 2950 (w), 2926 (w), 2916 (m), 2896
( w), 2876 ( w), 2850 ( w), 2734 ( w), 2534 ( w), 1921 (w, CO
s e ch), 1828 (m, CO s e ch), 1819 ( s, CO s e ch), 1808 (sh, CO
s e ch), 1804 (s, CO s e ch) 1601 (w), 1586 ( s), 1573 (m), 1496
( w), 1485 ( w), 1466 (w), 1443 (sh), 1436 ( w), 1423 ( w), 1411
( w), 1380 ( w), 1205 (w), 1188 (w), 1163 (w), 1141 (w), 1097 (w),
1041 (sh), 1028 (m), 999 ( s), 816 ( w), 804 ( w), 786 (w), 756 ( w),
715 (sh), 703 ( w), 691 (w), 676 (w), 652 (w), 637 ( w), 617 (m), 599
( w), 555 (w), 531 ( w), 520 (w), 489 (m), 477 (sh), 469 (m), 454 (m),
430 (w), 422 (sh), 395 ( w), 375 ( w), 344 ( w), 325 ( w), 294 ( w),
269 (w), 255 ( w), 224 (w), 201 ( w), 184 (m), 157 (m), 138 (sh) cm1.
[Mo(CO)3(PNPhPE )] (2 c)
Following gene al p ocedu e B, he [Mo(CO)3(PNPhPE )] (2c) was
ob ained as beige solid (122 mg, 0.24 mmol, 44%). C ys als sui able
o x- ay analysis we e ob ained by slow e apo a ion o he
complex in dichlo ome hane.
Anal. Calcd C21H33P2O3NMo (505.4 g/mol): C 49.9, H 6.58, N 2.77; C
50.2, H 6.59, N 3.10.
Wiley VCH Mon ag, 28.08.2023
2399 / 317727 [S. 11/15] 1
Eu . J. Ino g. Chem. 2023, e202300280 (11 o 14) © 2023 The Au ho s. Eu opean Jou nal o Ino ganic Chemis y published by Wiley-VCH GmbH
Resea ch A icle
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61
Chap e 5 P ojec 3 - Su ace unc ionaliza ion o iden a e PNP and PPP Ligands
o he equa o ial ca bonyl ligands in he IRRA spec um as he dipoles a e no pa allel o
he su ace. As expec ed, he ica bonyl complex bea ing he ipod ligand showed global
desac i a ion o he ca bonyl ligands, due o he elec on wi hd awing p ope ies o he gold
su ace.
[262]
Jus as epo ed by Schlimm and S ucke he desac i a ion o he symme ical
A(1) s e ch was pa ially compensa ed. This was obse ed e en hough he ligand does no
ha e a conjuga ed π-sys em.[261,262]
Fig. 5.3:
Illus a ion o he molybdenum ica bonyl complex bea ing a modi ied ipodal P
3
ligand on
a Au(111) su ace. The complex is a ached o a TATA-pla o m which is used o e ically
deposi he sys em on he su ace.[262]
Besides pince and ipodal sys ems ha we e epo ed by ou g oup p e iously,
[261,262]
his
p ojec ocuses a ound he las class o ligands wi h h ee dono s. Aim o his p ojec was
he unc ionaliza ion o iden a e PEP (E = N, P) ligands o su ace chemis y. As in p io
p ojec s, he ligands a e o be coo dina ed o Mo(0) ica bonyl complexes as he s abili y o
he complexes has been in es iga ed in dep h and no coligands a e needed. A u he goal is
he elec ochemical in es iga ion and a possible sui abili y as a he e ogeneous ca alys . The
ligand chosen as iden a e coun e pa o pince sys ems was he PNPhPPh ligand ha was
pa o he second p ojec as well (c . P ojec 2, Chap e 4). Besides he PNP sys em a
PPP sys em analogous o he ipodal PPP sys em was designed. As a s a ing poin o he
pu ely phosphine based sys em, he iden a e p PP
H
P ligand was used, which is used by
ou g oup o he syn hesis o he pen aPod ligand (c . P ojec 1, Chap e 3). The gene al
composi ion o he sys ems is modi ied o i he abo e men ioned c i e ia: he ancho g oup,
he space and he head g oup. In o de o a ach he ligands o he gold su ace, a subs a e
speci ic ancho g oup is needed. Fo his, wo di e en app oaches we e chosen. One app oach
68

includes he in oduc ion o an ace ylene g oup which could be ei he a ached o a pla o m
as p esen ed in p e ious wo k o clicked o an azide unc ion o ming a iazole ing. The
azide needed o his cycloaddi ion is bound o he gold su ace ia an alkyl SAM wi h a hiol
g oup capable o o ming co alen bonds o he gold su ace (Figu e 5.4 op igh ). Besides he
o ma ion o a iazole ing by Huisgen’s cycloaddi ion
[263]
and a pla o m app oach (Figu e
5.4 op le ), he ligands could be modi ied wi h a g oup capable o binding o a subs a e.
One app oach o his is he u iliza ion a hiol unc ion as ancho g oup. The hiol g oup is
pa o a hiophenyl g oup included in he ligand backbone. The phenyl g oup now ac s as
he space g oup be ween he su ace and he complex (Sec ion 5.2, Figu e 5.4 igh ). Wi hin
he scope o his hesis, his app oach was only applied o a PNP ype ligand, and is he main
ocus o his p ojec .
Fig. 5.4:
Illus a ion o he app oaches o deposi ing a Mo(0) ica bonyl complex bea ing iden a e
PNP ligand on gold su ace a ge ed in his p ojec .
69
Chap e 5 P ojec 3 - Su ace unc ionaliza ion o iden a e PNP and PPP Ligands
5.1 Ace ylene unc ionaliza ion o he PNPhPPh ligand
As men ioned abo e, he PNP ligand chosen o he modi ica ions owa ds su ace a achable
sys ems was he PN
Ph
P
Ph
ligand. F om he s udy in he second p ojec (c . P ojec 2,
Chap e 4) he limi a ions o he PNP sys ems and hei s abili ies a e known, which led o
he decision ha diphenylphosphine dono s would be a well sui ed choice. No only a e hey
known o be good dono s ega ding molybdenum ica bonyl complexes, bu a e also he leas
sensi i e owa ds oxida ion om he lis o phosphines a ailable. As known om p e ious
expe iences in ou g oup, he sys ems will be exposed o some oxygen du ing p epa a ion
o he su ace ac i e spec oscopies. Ei he om ans e in o he sample chambe o om
oxygen/wa e adso bed on he su ace o he wai e .
NOH
HO NClCl NClCl
B
1. POCl3
e lux, 6 h
2. H2O
[Bu4N][B 3]
dcm, 0 °C
CuI, [Pd(PPh3)4]
TMSA, NE 3
115 °C, 3 d
NClCl
Si
NPP
Si
n-BuLi, h , 0 °C
2 eq. HPPh2
1
2
3
4
Scheme 1:
Syn he ic access o he su ace modi ied PN
Ph
P
Ph
ligand 4.TMSA = T ime hylsilylace y-
lene.
S a ing om N-phenyldie hanolamine chlo ina ion o he hyd oxy g oups ga e N,N-bis(2-
chlo oe hyl)aniline (1). This was done by a modi ied me hod based on he p ocedu e by
H ishikesan e al.
[264]
A e he eac ion was comple ed, excess phospho us oxychlo ide was
ca e ully neu alized wi h wa e . Cooling he eac ion mix u e using an ice ba h supp esses
70
5.1 Ace ylene unc ionaliza ion o he PNPhPPh ligand
he neu aliza ion, leading o a spon aneous and a he iolen eac ion upon wa ming o
oom empe a u e, why a wa e ba h a oom empe a u e was used as coolan . This syn hesis
was also a emp ed using hionyl chlo ide, howe e no p oduc could be ob ained. The
comple eness o he con e sion om he alcohol o he chlo ide (1) was con i med by NMR
and IR spec oscopy. Especially he in a ed spec um showed he success ul con e sion as no
cha ac e is ic OH s e ches we e ound.
In o de o in oduce he ace ylene unc ion, he phenyl ing on he aniline was b omina ed
in he 4-posi ion, yielding 4-b omo-N,N-bis(2-chlo oe hyl)aniline (2). This was achie ed by
ollowing he p ocedu e desc ibed by Hu man e al.,
[265]
howe e he eac ion was cooled o
0°C ins ead o 10 °C. The c ude p oduc was dissol ed in me hanol and c ys allized in he
eeze (-32 °C). The solid was il e ed and sol ed in me hanol again o dec ease he amoun
o [n-Bu
4
N]
+
sal s om he p oduc . In o de o ully emo e he sal s he c ude p oduc was
ec ys allized om me hanol and he desi ed compound 2was ob ained as ligh pink solid.
In oduc ion o he ace ylene g oup was achi ed by Sonogashi a coupling
[266]
o compound
2 o ob ain N,N-bis(2-chlo oe hyl)-4-(( ime hylsilyl)e hynyl)aniline (3). Mul iple a emp s
we e made in o de o ob ain he desi ed p oduc . The i s a emp s had a eac ion ime o
5 d, which was la e educed o 3 d. Fu he mo e, he ca alys was a ied and changed om
[
PdCl2(PPh3)2
] o [
Pd(PPh3)4
].
[266,267]
A e column ch oma og aphy using n-hexane and
e hyl ace a e (4:1) he p ecu so o ligand 4was ob ained as da k o ange oil. F om he NMR
spec a i became e iden ha , al hough pu i ied by column ch oma og aphy, small impu i ies
emained. None heless, he in oduc ion o he TMS-ace ylene g oup was obse ed in he
1
H- and
13
C NMR spec a. Despi e small impu i ies he p ecu so o he ligand was u he
eac ed using he well es ablished ou e o he in oduc ion o he seconda y phosphines wi h
n-bu ylli hium and subsequen pu i ica ion by il a ion o e Celi e
®
and basic aluminum
oxide.
[216–218,268]
This yielded he desi ed p oduc N,N-bis(2-(diphenylphosphino)e hyl)-4-
(( ime hylsilyl)e hynyl)aniline (4) as highly iscous o ange oil (44%).
71
Chap e 5 P ojec 3 - Su ace unc ionaliza ion o iden a e PNP and PPP Ligands
Fig. 5.5: 31
P
{1
H
}
NMR spec um o ligand 4. The success ul subs i u ion o he e minal chlo ides
by diphenyl phosphine can be seen om he p oduc signal a -21.1 ppm.
F om he
31
P NMR spec um (Figu e 5.5) he o ma ion o ligand 4was con i med. This is
indica ed by he signal a -21.1 ppm, which is known om he unmodi ied ligand. Beside he
main p oduc signal, hose o some byp oduc s we e ound as well. The signal a -40.0 ppm
can be assigned o excess diphenyl phosphine. Th ee o he small impu i ies we e ound a
-23.0 ppm, -20.9 ppm and -14.5 ppm which could no be iden i ied bu can possibly assigned
o a singula subs i u ed p oduc as no all o he
HPPh2
has eac ed and po en ially some
decomposed p oduc . The o ma ion o a small byp oduc is also con i med om he
13
C
NMR spec um as a second, smalle se o signals is ound beside he p oduc signals o
he ligand. The ca bon a oms o he ace ylene uni on he o he hand a e only ound once.
Conside ing he sligh high ield shi o he signals, he byp oduc is ei he he phosphina ed
e sion o he b omina ed compound 2o he b omide as well as he chlo ide subs i uen s
we e exchanged by he li hium diphenyl phosphide.
As can be seen om he in eg als o he signals in he
31
P NMR spec um, he impu i ies a e
a he small, which is why he ligand was s ill been used o he coo dina ion o molybdenum
ica bonyl p ecu so s. The i s a emp s we e made using [Mo(CO)
3
(
η6
- oluene)] as p e-
cu so complex, due o he [Mo
(CO)3
(ch )] complex no being a ailable a ha ime. The
[Mo(CO)
3
(
η6
- oluene)] complex was syn hesized om [
Mo(CO)6
] a e modi ied p ocedu es
72
5.1 Ace ylene unc ionaliza ion o he PNPhPPh ligand
om Rybinskaya e al.
[269]
and Whi ing &Nicholls.
[270]
The [Mo(CO)
3
(
η6
- oluene)]
was chosen as he complex is less s able compa ed o he cyclohep a iene analogue and
mo e p one owa ds ligand exchange.
[271]
None heless, no eac ion was obse ed a oom
empe a u e. Due o his, a second a emp wi h inc eased empe a u e was made. This
lead o he o ma ion o a p ecipi a e, which was il e ed and washed. The IR spec um
(Figu e 5.6, black spec um) o he ob ained complex showed a mul i ude o CO s e ches,
indica ing a mix u e o complexes. Al hough he s e ches o he desi ed complexes a e isi-
ble as shoulde s, a pu i ica ion o he mix u e was no success ul and he a emp was disca ded.
Fig. 5.6:
Compa ison o he in a ed spec a o he [Mo
(CO)3
(PN
Ph
P
Ph
)] complex ( op, ed) o he
a emp ed coo dina ion o he su ace modi ied PNP ligand 4(bo om, black).
Du ing he expe imen al wo k o P ojec 2, some expe imen s we e conduc ed using [Mo(CO)
3
(
η6
-
oluene)]. None heless, he bes esul s we e achie ed using he cyclohep a iene molybdenum
ica bonyl complex and as i was no comme cially a ailable a he ime, i was syn he-
sized om
Mo(CO)6
. The i s app oach o he syn hesis was ca ied ou by ollowing a
sligh ly modi ied p ocedu e o Bisne e e al.
[272]
Re luxing
Mo(CO)6
in d y n-oc ane and
cyclohepa iene (ch ) ga e a da k ed solu ion. Remo al o he sol en and ch has o be
pe o med wi h ex em cau ion and he empe a u e should no exceed 35 °C as he complex
would sublima e. The d ied c ude p oduc was hen ans e ed in o a Soxhle ex ac o
and ex ac ed using n-hexane. The sol en was emo ed ca e ully and he complex ob ained
as ed solid. Due o he poo yield o he Soxhle ex ac ion, an al e na i e p ocedu e was
used o he isola ion and pu i ica ion o he complex du ing a second un. A e e lux and
73

Chap e 5 P ojec 3 - Su ace unc ionaliza ion o iden a e PNP and PPP Ligands
emo al o he ola ile componen s, he [Mo
(CO)3
(ch )] complex was ex ac ed om he c ude
p oduc upon addi ion o n-hexane. This s ep was epea ed mul iple imes un il he sol en
did no dyed ed anymo e. This s ep emo ed some pa s o un eac ed
Mo(CO)6
, he es
was emo ed ia sublima ion. The empe a u e applied should no exceed 30 °C o assu e
he sublima ed compound is he hexaca bonyl only. This p ocess is e y ime consuming bu
yields a e y pu e p oduc . Un o una ely, bo h p ocedu es esul ed e y poo yields. The
poo yield can be a ibu ed o he
Mo(CO)6
sublima ing du ing he e lux in he i s s ep o
he eac ion. Clausen was able o imp o e he yield by changing he appa a us and building
a cus om spa ula and sc aping he sublima ed
Mo(CO)6
back in o he solu ion. In addi ion
o ha he eac ion ime was signi ican ly elonga ed.[273]
Using he [Mo
(CO)3
(ch )] complex, ano he a emp o coo dina e he su ace modi ied
PN
Ph
P
Ph
ligand (4) was made. A success ul coo dina ion o he PNP ligands o he Mo(CO)
3
agmen should esul in he p ecipi a ion o a yellowish/beige solid. Using iden ical condi ions
o he coo dina ion as used o he unmodi ied ligand, he solu ion emained unchanged. Due
o his, he empe a u e was inc eased o 50 °C o 6 h and a e wa ds s i ed o ano he
12 h. This esul ed in a da kening o he solu ion bu no o he o ma ion o he an icipa ed
yellowish solid, which was obse ed o nea ly all molybdenum ica bonyl complexes bea ing
PNP ligands in P ojec 2. None heless, he sol en was emo ed and he c ude p oduc washed
mul iple imes wi h n-pen ane o emo e ligand and p ecu so complex. The emaining solid
was washed and d ied. The syn hesis esul ed again in a mix u e o complexes. Al hough he
desi ed complex was con ained in he p oduc mix u e, mul iple side eac ions occu ed as
can be seen om 31P NMR spec um (Figu e 5.7)
74
5.1 Ace ylene unc ionaliza ion o he PNPhPPh ligand
Fig. 5.7: 31
P
{1
H
}
NMR spec um o he a emp ed coo dina ion o he su ace modi ied PN
Ph
P
Ph
ligand 4using [Mo(CO)3(ch )].
F om compa ison o he spec um o he unmodi ied PN
Ph
P
Ph
ligand i can be seen ha he
desi ed complex was o med bu many o he species as well. By compa ing wi h he li e a u e,
he signal a 25 ppm can be assigned o he e aca bonyl complex wi h he phosphines
coo dina ed.
[274]
The e aca bonyl complex is he p oduc o a decomposi ion eac ion o
he desi ed complex. This can possibly be e aced o he inc eased empe a u es applied.
The desi ed p oduc is expec ed a a ound 40 ppm. As can be seen om Figu e 5.7, mul iple
species we e ound, indica ing he o ma ion o mul iple ica bonyl complexes wi h acial
geome y. This leads o he conclusion ha he ligand decomposed o a ce ain deg ee as well.
Un o una ely, he desi ed ca bonyl complex could no be isola ed bu should be ob ainable
unde di e en condi ions e.g. elonga ion o eac ion imes, di e en sol en s and lowe
empe a u es. Al hough he a emp s made a e e y p omising and ligand 4was syn hesized
success ully, he main ocus was edi ec ed o ano he a ian o he PN
Ph
P
Ph
ligand ha
ea u es a hio-based ancho g oup.
75
Chap e 5 P ojec 3 - Su ace unc ionaliza ion o iden a e PNP and PPP Ligands
5.2 Thio unc ionaliza ion o he PNPhPPh ligand
The second a ian o a su ace unc ionalized PNP ligand ea u es a hiol ancho g oup.
This al e na i e app oach is ano he a emp con inuing on om he esul p esen ed in he
second p ojec o his hesis. The sul u ancho is chosen in o de o c ea e a di ec co alen
bond be ween he sys em and he gold su ace. Sul u is an excellen choice when he su ace
aimed o is gold as he au ophillic cha ac e o he sul u helps wi h he o ma ion o s able
bonds.
[275]
The i s s eps o he eac ion a e simila o he ones o he ace ylene unc ionalized
PNP ligand.
N
SCN
Cl
Cl
N
SCN
PPh2
Ph2Pn-BuLi
0°C, h
2 eq. HPPh2
1. B 2, NaB
2. NH4SCN
NClCl
NOHHO
e lux, 6 h
POCl3
d y MeOH
[Mo(CO)3(ch )]
oluene, oom emp.
E 2O, 0°C
LiAlH4
Mo
Ph2P
Ph2PCO
CO
CO
N
SCN
Mo
Ph2P
Ph2PCO
CO
CO
N
SH
1
5
6
7
8
Scheme 2:
Syn he ic access o hiocyana e- unc ionalized PN
Ph
P
Ph
ligand (6) and he co esponding
ica bonyl complex 7. He ein he SCN g oup ac s as p o ec i e g oup du ing he
coo dina ion and is con e ed o a su ace ac i e hiol ia educ ion.
The i s s ep is a chlo ina ion ollowing he p ocedu e desc ibed in he sec ions 4.1 and 5.1
esul ing he PNP p ecu so 1. The sul u ancho is in oduced as hiocyana e which was
chosen o mul iple easons. The i s eason is ha he in oduc ion o a hiocyana e g oup
76
5.2 Thio unc ionaliza ion o he PNPhPPh ligand
is a well es ablished syn hesis and is selec i e owa ds he pa a-posi ion o he amine. The
second eason is ha he hiocyana e g oup enables wo me hods o a achmen o he gold
su ace. The i s in ol es educ ion o a hiol and subsequen binding o he su ace (scheme
2) while he second me hod is a di ec a achmen upon a gold induced CN
-
elease.
[276]
The
in oduc ion o he SCN g oup is a wo s ep eac ion (Scheme 3). In he i s s ep o he
eac ion a b omine is in oduced in he 4-posi ion. This can be done in wo ways: ei he by
ollowing he Hu man p ocedu e
[265]
desc ibed in sec ion 5.1 using [NBu
4
][B
3
] o ollowing
he ins uc ions o C eigh on e al. gene a ing he eac i e B
3-
ion in si u om b omine and
sodium b omine in d y me hanol and adding i o a solu ion o 1and ammonium hiocyana e.
The i s a ian wo ks bes when isola ing he 4-b omo-N,N-bis(2-chlo oe hyl)aniline (2),
dissol ing i in me hanol and adding pu e
NH4SCN
. The p oduc can be ec ys allized om
e hanol. The ad an age o he second me hod is ha i is a one-s ep syn hesis. The c ude
p oduc o he syn hesis is a b own oil, which is bes pu i ied by ec ys alliza ion om e hanol.
Bo h me hods we e ied, bo h leading o a success ul isola ion o he desi ed p oduc in good
yields.
N
Cl Cl N
Cl Cl
B
N
Cl Cl
SCN
NH4SCN
MeOH
[NBu4][B 3]
dcm
1. B 2, NaB
2. NH4SCN
MeOH
125
Scheme 3:
Illus a ion o he wo me hods used o in oduce he hiocyana e g oup in o he ligand
p ecu so .
N,N-bis(2-chlo oe hyl)-4- hiocyana oaniline (5) is an ideal dummy molecule in o de in es-
iga e and op imize he di ec deposi ion upon CN
-
elease on a gold subs a e. The main
disad an age is ha in es iga ions wi h IRRAS a e p oblema ic as no good indica o ega ding
he su ace o ien a ion is p esen in he molecule. None heless, i s a emp s ega ding a di ec
deposi ion ha e been made. Al hough he p epa a ion me hod s ill equi es op imiza ion, i
was ound ha a i s a emp o he di ec deposi ion wo ked o some ex en as can be seen
om he XP spec a (Figu e 5.8).
77
Chap e 5 P ojec 3 - Su ace unc ionaliza ion o iden a e PNP and PPP Ligands
Fig. 5.10:
Compa ison o he a oma ic egion o he
13
C
{1
H
}
NMR spec a o he PN
Ph
P
Ph
ligand
( op) and he bo ane p o ec ed PN
Ph
P
Ph
a e he in oduc ion o he hiocyana e g oup
(bo om). The in oduc ion o he SCN g oup leads o a shi o he wo me a ca bons
(blue a ow) and he pa a-ca bon ( ed a ow) o he aniline ing.
The
13
C NMR spec um shows he success ul in oduc ion o he SCN g oup in o he PN
Ph
P
Ph
gi ing he ligand p ecu so 11. Fu he mo e, he
31
P NMR spec um shows ha he halo-
gena ion o he phosphines is only obse ed as mino side eac ion and he bo ane p o ec ion
has wi hs ood he eac ion condi ions, especially he elease o B 2(Figu e 5.11, bo om).
84

5.2 Thio unc ionaliza ion o he PNPhPPh ligand
Fig. 5.11:
Compa ison o he
31
P
{1
H
}
NMR spec a o he PN
Ph
P
Ph
ligand (9, op), he bo ane
p o ec ed PN
Ph
P
Ph
ligand (10, middle) and he bo ane p o ec ed PN
Ph
P
Ph
a e he
in oduc ion o he hiocyana e g oup (11, bo om). The bo ane g oups success ully
wi hs ood he eac ion condi ions du ing he in oduc ion o he SCN g oup.
Besides he main p oduc one small, b oad signal is isible as well as wo small, low ield
shi ed signals. The inal s ep in he ligand syn hesis is he emo al o he bo ane g oups.
The common way o emo e hem is by use o mo pholine and empe a u e. The ligand
p ecu so 11 was e luxed in mo pholine and subsequen ly s i ed a 90 °C o 3 d. The
condi ions applied un o una ely lead o he o ma ion o a mix u e o p oduc s as can be
seen om he
31
P NMR spec um (Figu e 5.12). The p oduc s o med can be assigned o
di e en species. The desi ed p oduc 6, a small ac ion o he ligand wi h one b omina ed
phosphine g oup and one non-halogena ed phosphine. Fu he mo e, ou addi ional signals
appea ed be ween 30.6 and 30.3 ppm. These signals may be associa ed wi h phosphine
oxide a ian s o med du ing he a emp ed emo al o he p o ec i e g oup. The signals
ound could be assigned o di e en combina ions o ully oxidized phosphines, wi h only one
phosphine oxide and a mino combina ion o an oxidized and a halogena ed phosphine. This
85
Chap e 5 P ojec 3 - Su ace unc ionaliza ion o iden a e PNP and PPP Ligands
assump ion is based on he
31
P NMR shi s epo ed o di e en molecules based a ound
unc ionalized e hyldiphenylphosphine oxides.
[283]
The o ma ion o he oxides indica es ha ,
al hough Schlenk condi ions we e applied, he phosphines mus ha e been exposed o oxygen.
This is p obably due o insu icien degassing o he mo pholine p io o use.
Fig. 5.12: 31
P
{1
H
}
NMR spec um o he a emp ed emo al o he bo ane g oups on SCN modi ied
PN
Ph
P
Ph
ligand (11). Besides he o ma ion o he p oduc and he halogena ed phosphines
om he p io s ep mainly phosphine oxides we e o med.
Al hough he ligand a ian wi h phosphine oxides would no coo dina e, no coo dina ion
a emp was pe o med, as only a e y small pa o he p oduc ob ained can be assigned o
he desi ed PN
Ph-SCN
P
Ph
ligand (6). None heless, his ou e is e y p omising and should be
epea ed wi h some a ia ions o he eac ion condi ions and ho oughly degassed mo pholine.
Besides he use o mo pholine as emo al agen o he p o ec i e g oups, a di e en amine
like ie hylamine could be ied.
86
5.3 Func ionaliza ion o he p PPHP-ligand
5.3 Func ionaliza ion o he p PPHP-ligand
Besides he e o ds sou ounding he su ace modi ica ions o he PNP ligand, a emp s we e
made o modi y a well known building block om he pen aPod syn hesis - he p PPHP. The
ligand was supposed o ep esen he iden a e PPP coun e pa o he al eady success ul
deposi ed ipodal
P3
sys em by Pe e sen e al.
[262]
The unde lying syn he ic ou e is
based on a modula sys em (Scheme 6). The syn hesis o he p PPHP ligand
[145,231]
is well
es ablished in ou g oup and halogen-con aining building blocks ha no only ha e he
app op ia e ancho g oup, bu also he desi ed space a e comme cially a ailable. In line wi h
he p ojec s al eady p esen ed, he iden a e PPP sys em was also o be equipped wi h an
ace ylene uni o bind o a pla o m o an alkyl-SAM o su ace ixa ion.
n-BuLi
0°C, h
P
H
Ph2PPPh2
PPh2PPPh2
TMS
X
TMS
+
X = F, Cl, B
12
13
Scheme 6:
Reac ion scheme o he modula assembly o he su ace-modi ied p PPHP ligand (13)
based on he p PPHP ligand (12) and he ((4-halogenephenyl)e hynyl) ime hylsilane.
The idea behind his ou e was o apply known subs i u ion o halogens by phosphines.
Following he well es ablished ou e he p PPHP ligand was syn hesized. In a i s a emp
he p PPHP ligand was dissol ed in h and n-BuLi was added. Pa allel o ha , he ((4-
chlo ophenyl)e hynyl) ime hylsilane was dissol ed in h and subsequen ly added d opwise
o he p PPHP solu ion. The esul o his eac ion was a mix u e o mul iple species. As
he e minal phenyl phosphines a e qui e esis an o ai an a emp was made o pu i y he
desi ed p oduc using column ch oma og aphy. F om he
31
P NMR spec um o he isola ed
p oduc i can be seen ha he wo building blocks we e connec ed success ully (Figu e 5.13,
bo om).
87
Chap e 5 P ojec 3 - Su ace unc ionaliza ion o iden a e PNP and PPP Ligands
Fig. 5.13:
Compa ison o he
31
P
{1
H
}
NMR spec um o he p PPHP ligand ( op) and he modi ied
ligand 13 (bo om). The enla ged egions show se e al byp oduc s and oxidized species.
The la ge signal a -17.0 ppm can be assigned o he PPh
2
g oups and he signal a
-26.1 ppm o he cen al phosphine a e he subs i u ion o he p o on by he a oma ic
esidue.
As can be seen om he op spec um, he cen al PH o he p PPHP ligand can be ound a
-72.7 ppm. A e he eac ion he signal o he cen al phospho us shi ed o -26.1 ppm due
he subs i u ion o he hyd ogen by he a oma ic esidue. None heless, mul iple by-p oduc s
we e s ill ound in he p oduc mix u e. Since a second a emp a column ch oma og aphic
pu i ica ion was deemed unlikely o be success ul, due o epea ed exposu e o oxygen, a
coo dina ion a emp was s a ed despi e he lack o pu i y in he hope ha his would yield
a pu e p oduc . The impu e ligand was added o he [Mo
(CO)3
(ch )] p ecu so complex. As
i was al eady obse ed o he ica bonyl complexes wi h PNP ligands, he coo dina ion was
88
5.3 Func ionaliza ion o he p PPHP-ligand
indica ed by a colo change om deep ed o yellow/beige. Al hough he yield was poo , a
solid was isola ed. Fo analysis ia NMR spec oscopy, he solid was dissol ed in DCM, which
led o he o ma ion o an insoluble black solid and hus o he p esumed decomposi ion o he
p oduc . Fu he mo e, an IR spec um o he isola ed p oduc was measu ed. Al hough he
colo o he solid looked p omising, he spec um showed ha he desi ed ica bonyl complex
was no ob ained, because no ib a ions we e ound in he CO s e ching equency egion.
By modi ying he syn hesis pa ame e s and subs i u ing he chlo ine-based building block wi h
a b omina ed and lou ina ed analogue, he objec i e was o syn hesize he pu e ligand. The
syn hesis was ca ied ou unde he same eac ion condi ions as in he p e ious expe imen .
Un o una ely, he desi ed ligand was no ob ained. In subsequen a emp s he empe a u es
we e a ied and he n-BuLi was subs i u ed by li hium diisop opylamide which also did no
p o ide he desi ed esul s. In pa allel wi h e o s o syn hesize he p PP
Ph-ace ylene-TMS
P
ligand (13), he success ul syn hesis o he e hyl-b idged analog was demons a ed by ou
g oup.
[284]
I was ound ha in o de o ob ain a pu e p oduc , a halogen a om is equi ed
as subs i uen on he cen al phosphine. None heless, i was also demons a ed ha he
linking o he p PPHP ligand and he ((4-chlo ophenyl)e hynyl) ime hylsilane is possible in
p inciple.
89

Chap e 6
Conclusion & Ou look
This hesis is spli in o h ee main p ojec s. The i s ocuses a ound he di e en beha io o
he [
W(N2)
(P
2Me
PP
2Ph
)] complex compa ed o i s molybdenum analogue. The in es iga ions
we e based a ound he assump ion ha he complexes ha e di e en edox po en ials, why
he main ocus e ol ed a ound elec ochemis y. The second s udy p o ides an in-dep h
in es iga ion ega ding he coo dina ion beha io o di e en iden a e PNP ligands. All
PNP ligands we e coo dina ed o molybdenum ica bonyl complexes, due o hei excellen
spec oscopic p ope ies. Gaining a be e unde s anding o hese sys ems is bene icial o he
inal p ojec o his hesis, which deals wi h he syn hesis and cha ac e iza ion o molybdenum
ica bonyl complexes bea ing iden a e PNP ligands wi h unc ionaliza ion o su ace
deposi ion. This p ojec aims o con inue he wo k o S ucke,Schlimm and Pe e sen e
al., which al eady demons a ed he deposi ion o molybdenum ica bonyl complexes wi h
pince and ipodal ligands on su aces.[261,262]
6.1 P ojec 1
The i s p ojec was ocused on syn he ic ni ogen ixa ion wi h he pen aPod ligand and a
con inua ion o a p io s udy by Engesse e al., which demons a ed he ca aly ic ac i i y o
he molybdenum dini ogen complex bea ing he pen aPod and i s supe io i y compa ed o he
egula dini ogen complexes wi h pen aphosphine coo dina ion sphe es p o ided by i- and
biden a e phosphine ligands. As he molybdenum complex was ca aly ically ac i e, he nex
s ep in es ing he capabili y o he ligand was he coo dina ion o al e na i e me al cen e .
As ungs en is usually he me al o choice when exchanging molybdenum, he pen aPod
was coo dina ed on ungs en and in es iga ed ega ding i s ac i i y owa ds de i a iza ion
and ammonia o ma ion. This p ojec was execu ed in collabo a ion wi h Junge and he
pen aPod ligand was success ully coo dina ed and he ungs en mono-dini ogen complex
isola ed. The esul ing [W
N2
(pen aPod)] complex was cha ac e ized using IR, Raman and
NMR spec oscopy. Besides an expec ed shi o lowe wa enumbe s o he
N2
-s e ch and
addi ional sa elli es in he
31
P-NMR spec um, he spec a as well as he c ys al s uc u e
we e su p isingly simila o he molybdenum analogue. In es iga ions ega ding he ca aly ic
ac i i y owa ds ammonia o ma ion o he [
W(N2)
(P
2Me
PP
2Ph
)] complex in he p esence
o sama ium diiodide / wa e esul ed in 2.75 equi . Al hough he ac i i y was ound o be
well below he esul s o he molybdenum complex, his is he i s example o a ungs en
91
Chap e 6 Conclusion & Ou look
dini ogen complex capable o gene a ing mo e han wo equi alen s o ammonia. In o de
o in es iga e he di e ences o he complexes, elec ochemical and spec oelec ochemical
s udies we e pe o med. The molybdenum as well as he ungs en complex we e in es iga ed
by cyclic ol amme y. The c s ound o he complexes we e e y simila . E
1/2
o he i s
edox sys ems we e de e mined a -1.16 V o he ungs en and a -1.13 V o he molybdenum
complex, espec i ely. None heless he e e sibili y o he 0
⇄
+I sys em di e s, as he
ungs en complex was ound o be ully e e sible unlike he molybdenum complex, which was
only pa ly e e sible. Fo he second oxida ion sys ems e y simila E
1/2
alues we e ound
as well, ye he e e sibili y di e ed. Bo h sys ems we e i e e sible a low scan a es, bu an
inc ease in e e sibili y was obse ed o he ungs en complex as he scan a e was inc eased.
Fu he analysis o he peak cu en unc ion using Randles-Se cik equa ion e ealed an ECE
ype mechanism o he ungs en complex. Deepe in es iga ions in o he species o med
upon oxida ion we e ca ied ou by means o IR-spec oelec ochemical in es iga ions. I
was ound ha he [
W(N2)
(P
2Me
PP
2Ph
)]
+
complex was mo e s able han he molybdenum
analogue, which eleased he dini ogen ligand upon oxida ion. Due o he highe s abili y o
he oxidized complex he ungs en-N2complex was obse ed.
Following his p ojec Junge e al. p esen ed an ex ensi e heo e ical s udy ega ding
possible mechanisms o he
NH3
o ma ion and he compe ing hyd ogen e olu ion eac-
ion.
[230]
F om p e ious a emp s wi hin he amewo k o his hesis, i was ound ha no
signi ican amoun s o ammonia we e gene a ed elec oca aly ically upon addi ion o acids
(c . sec ion 3.2). Fu he expe imen al in es iga ions ega ding his opic could be based on
he success in elec oca aly ic ammonia o ma ion p esen ed by he Pe e s g oup.
[173]
They
demons a ed ha he ca aly ic ac i i y o a ungs en complex can be achie ed by adding a
media o ha ac s as a PCET agen .
6.2 P ojec 2
The second and main p ojec o his hesis was he in es iga ion o he coo dina ion beha io
o iden a e PNP ligands on molybdenum ica bonyl sys ems. The scope was o in es iga e
he in luence o phosphines and hei subs i u es on coo dina ion beha io and s abili y. Fo
his, a iden a e ligand wi h cen al aniline dono was chosen in e e ence o he well s udied
pince ligands. A se ies o iden a e PN
Ph
P
R
ligands (R = Ph, Me, E , Pln, Cyp,
i
P , Cy,
Bu) was syn hesized and coo dina ed o he [Mo(CO)
3
(ch )] p ecu so . All ligands we e
success ully syn hesized bu no all complexes could be ob ained. Complexes bea ing he
PN
Ph
P
Me
, PN
Ph
Pln and PN
Ph
P
Bu
could no be isola ed. All o he complexes we e isola ed
and ho oughly cha ac e ized. F om IR- and Raman spec a i became appa en ha all
complexes adap ed a acial geome y in he solid s a e. This was expec ed as he p ecu so
92
6.2 P ojec 2
p ede ined a acial coo dina ion geome y. The acial geome y was also ound in solu ion o
all complexes, which was de e mined om he shi o he signals in he
31
P NMR spec a
as well as he ABX pa e n ound o he equa o ial CO ligands in he
13
C NMR spec a.
None heless, he me idional isome was ound as mino byp oduc (<1%).
Compa ison o simila sys ems (NH ins ead o NPh) in he li e a u e e ealed ha he
geome y o he complexes shi ed om a acial o a me idional geome y wi h inc easing
s e ic demand o he phosphines subs i uen s. DFT s udies we e pe o med in o de o gain
insigh s in o he isome iza ion mechanism and he disc epancies be ween he wo sys ems.
Isodesmic calcula ions o he ela i e ligand exchange ene gies e ealed a con adic ion o he
expe imen al esul s o he sys ems con aining NPh as he me idional isome is ene ge ically
a o ed o bulky phosphines. Fo he sys ems wi h NH, he calcula ions ag ee well wi h he
expe imen al obse a ions. Wha became clea , howe e , is ha he molybdenum ica bonyl
complex bea ing he PNPhP Bu ligand was ene ge ically un a o able in he acial and me id-
ional geome y. None heless, in he calcula ions no salien di e ence c ys allized be ween he
NPh and NH sys ems ha would explain he di e en beha io , excluding he modynamics
as he cause o he obse ed geome ies. Fu he calcula ions ega ding he kine ics we e
pe o med in o de o in es iga e he isome iza ion mechanism. Two possible pa hways we e
ound. The i s is a di ec isome iza ion in which one isome ans o ms in o he o he o e a
ansi ion s a e. The ansi ion s a e du ing di ec isome iza ion p o ed o be ene ge ically
un a o able and also showed no signi ican di e ences. The second pa hway in ol es he
dissocia ion o a CO ligand p io o he isome ic ans o ma ion. This pa hway indeed e ealed
di e ences be ween he wo sys ems. Fo he ans o ma ion o he NH sys em he ansi ion
s a e be ween he acial and me idional s a e (s a ing om he dica bonyl a ian ) was ound
o be ene ge ically lowe compa ed o he NPh complex. Fu he mo e, a second, low lying
ansi ion s a e be ween wo con o me s o he me idional isome was ound o he NH sys em.
O hese wo only one belongs o he con e sion o he acial and he me idional isome s
in o each o he . The highe ene gies o he NPh sys em can be explained by he o ma ion
o an agos ic hyd ogen bond be ween he phenyl ing and he molybdenum, s abilizing he
pen acoo dina ed species, which needs o be b oken du ing he isome iza ion, he e o e leading
o an highe ene gy ba ie , hence inhibi ing he isome ic ans o ma ion.
The expe imen al esul s o he complexes bea ing PN
Ph
P ligands we e ob ained due o
he ac-p eo ien a ion caused by he cyclohepa iene p ecu so . Subsequen in es iga ions
include he subs i u ion o his p ecu so by a complex wi h p io me idional ligand a ange-
men o no p ede e mined o ien a ion like he u iliza ion o molybdenum hexaca bonyl as
demons a ed by Belle e al.
[285,286]
Al hough high empe a u es a e equi ed o his
syn hesis, Mo(CO)
6
does no dic a e a p e e ed coo dina ion geome y, which could allow o
he o ma ion o he me idional isome s o ligands wi h bulky phosphines. Ano he possibili y
would be o coo dina e he ligands o a molybdenum dica bonyl complex, gene a ing he
93
Chap e 7 Expe imen al Sec ion
13
C-NMR (125
MHz
,
CDCl3
, 300
K
):
δ
=146 (s, 1 C, C-3), 134 (s, 2 C, C-4), 114 (s, 2 C,
C-5), 111 (s, 1 C, C-6 ), 106 (s, 1 C, C-10 ), 92.2 (s, 1 C, C-9), 53.4 (s, 2 C, C-1), 40.4 (s, 2 C,
C-2), 0.30 (s, 3 C, C-11) ppm.
7.4 N,N-Bis(2-(diphenylphosphanyl)e hyl)-4-
(( ime hylsilyl)e hynyl)aniline
NClCl
Si
NP
P
Si
n-BuLi, h , 0 °C
2 eq. HPPh2
3
4
N,N-bis(2-chlo oe hyl)-4-(( ime hylsilyl)e hinyl)aniline (3, 440 mg, 1.34 mmol) was dissol ed
in h (10 mL). In a second essel, diphenyl phosphine (521 mg, 2.80 mmol) was dissol ed in
h (10 mL) as well and bo h solu ions cooled o 0 °C. To he diphenyl phosphine solu ion,
n-buli (1.2 mL, 3.14 mmol) was added d opwise and s i ed o 30 min. A e wa ds, he
solu ion wi h he ligand p ecu so 3was added slowly o he phosphine solu ion and s i ed
o 4 d a oom empe a u e. The sol en as well as excess n-buli we e emo ed in acuo. The
esidue was dissol ed in die hyl e he and il e ed h ough basic aluminum oxid and Celi e
®
.
The p oduc was ob ained as iscous o ange oil.
Yield: 360 mg (0.59 mmol) 44 %
100

7.4 N,N-Bis(2-(diphenylphosphanyl)e hyl)-4-(( ime hylsilyl)e hynyl)aniline
1
2
3
4
567
8
9
NP
P
Si
10
11
12
13
1
H-NMR (400
MHz
,
CDCl3
, 300
K
):
δ
=7.31-7.26 (m, 8 H, H-11), 7.22-7.16 (m, 12 H,
H-12/H-13), 7.09-7.05 (m, 2 H, H-5), 7.02-7.00 (m, 2 H, H-4), 3.25-3.17 (m, 4 H, H-2),
2.17-2.12 (m, 4 H, H-1), 0.12 (m, 9 H, H-9) ppm.
13
C-NMR (100
MHz
,
CDCl3
, 300
K
):
δ
=147.7 (s, 1 C, C-3), 138.8 (d, J
CP
= 12.3 Hz,
4 C, C-10), 133.3 (s, 2 C, C-4), 132.8 (d, J
CP
= 18.9 Hz, 8 C, C-11), 128.9 (s, 4 C, C-13),
128.6 (d, J
CP
= 6.76 Hz, 8 C, C-12), 111.5 (s, 2C, C-5), 109.8 (s, 1 C, C-6), 106.5 (s, 1 C,
C-7), 91.3 (s, 1 C, C-8), 47.7 (d, J
CP
= 25.6 Hz, 2 C, C-2), 26.2 (d, J
CP
= 14.4 Hz, 2 C,
C-1), 0.37 (s, 3 C, C-9) ppm.
31P-NMR (162 MHz, CDCl3, 300 K, H3PO4): -21.9 (s, 2P, PPh2) ppm.
101
Chap e 7 Expe imen al Sec ion
7.5 N,N-Bis(2-chlo oe hyl)-4- hiocyana oaniline
N
SCN
ClCl
1. B 2, NaB
2. NH4SCN
NCl
Cl
d y MeOH
1
5
N,N-Bis(2-chlo oe hyl)aniline (1, 2.00 g, 9.17 mmol) and ammonium hiocyana e (1.5 g,
19.7 mmol) we e dissol ed in me hanol (30 mL). The solu ion was cooled o 0 °C and a second
solu ion o b omine (0.5 mL) and sodium b omide (0.5 g) dissol ed in me hanol (5 mL), was
added d op wise. The solu ion was s i ed o 10 min a 0 °C, be o e pou ed in o deionized
wa e (100 mL). This s ep was supposed o p ecipi a e he desi ed p oduc , howe e , he c ude
p oduc immedia ely dissol ed again. Due o his, he solu ion was ex ac ed wi h die hyl
e he (3x 100 mL) and washed wi h sodium hiosul a e o emo e excess b omine. The o ganic
laye was d ied o e anhyd ous magnesium sul a e and he sol en emo ed. The esul ing
da k oil was ec ys allized om e hanol yielding he desi ed p oduc as whi e solid.
Yield: 1.39 (5.05 mmol) 55 %
N
Cl Cl N
Cl Cl
SCN
TBAB 3, NH4SCN
DCM, MeOH, 0 °C
1
5
A second me hod was used in o de o syn hesize he N,N -Bis(2-chlo oe hyl)-4- hiocyana oaniline
(5). Fo his, N,N-Bis(2-chlo oe hyl)aniline (1, 2.00 g, 9.17 mmol) and ammonium hiocyana e
(1.5 g, 19.7 mmol) we e dissol ed in a mix u e o me hanol (30 ml) and dichlo ome hane
(10 mL). The solu ion was cooled o 0 °C and a solu ion o TBAB
3
(4.42 g, 9.17 mmol)
dissol ed in DCM (10 mL) was added. The solu ion was s i ed o 10 min a 0 °C and ano he
30 min a oom empe a u e. The solu ion was washed wi h sodium hiosul a e solu ion and
d ied using magnesium sul a e. The sol en was emo ed and he c ude p oduc ec ys allized
102
7.6 N,N-Bis(2-(diphenylphosphino)e hyl)aniline-bo ane-complex
om me hanol. The ec ys alliza ion was epea ed wice in o de o emo e all ammonium
sal s.
Yield: 1.44 g (5.23 mmol) 57 %
1
2
3
4
56
7
N
Cl Cl
SCN
1
H-NMR (400
MHz
,
CDCl3
, 300
K
):
δ
=7.48-7.44 (m, 2 H, H-4), 6.72-6.68 (m, 2 H, H-5),
3.79-3.75 (m, 4 H, H-2), 3.66-3.62 (m, 4 H, H-1) ppm.
13
C-NMR (125
MHz
,
CDCl3
, 300
K
):
δ
=148 (s, 1 C, C-3), 135 (s, 2 C, C-4), 113 (s, 2 C,
C-5), 112 (s, 1 C, C-6), 112 (s, 1 C, C-7), 53.4 (s, 2 C, C-2), 40.2 (s, 2 C, C-1) ppm.
7.6 N,N-Bis(2-(diphenylphosphino)e hyl)aniline-bo ane-complex
BH3 SMe2
N
Ph2P PPh2N
Ph2P PPh2
BH3BH3
MeOH
910
The PN
Ph
P
Ph
(9, 604 mg, 1.17 mmol) was dissol ed in DCM (15 mL) and he bo ane dime hyl
sul ide complex (340 mg, 4.47 mmol) was added. The solu ion was s i ed o 2 h a oom
empe a u e and all ola ile compounds emo ed in acuo. The p oduc was ob ained as
colo less solid.
Yield: 578 mg (1.06 mmol) 91 %
103
Chap e 7 Expe imen al Sec ion
1
2
3
4
56
78
9
NP
P
10
11 BH3
BH3
1
H-NMR (400
MHz
,
CDCl3
, 300
K
):
δ
=7.69-7.64 (m, 8 H, H-8), 7.60-7.58 (m, 2 H,
H-4), 7.53-7.41 (m, 12 H, H-9/H-10), 7.39-7.34 (m, 3 H, H-5/H-6), 3.47-3.38 (m, 4 H, H-2),
1.85-1.74 (m, 4 H, H-1), 1.24-0.50 (m, 6 H, H-11) ppm.
13
C-NMR (100
MHz
,
CDCl3
, 300
K
):
δ
=147.7 (s, 4 C, C-7), 145.7 (s, 1 C, C-3), 131.2-
130.7 (m, 8 C, C-8), 128.5 (s, 2 C, C-4), 128.1-127.8 (m, 8 C, C-9 ), 127.4 (s, 2 C, C-5 ), 123.2
(s, 4 C, C-10), 111.7 (s, 1 C, C-6), 60.7 (d, J
CP
= 9.27 Hz, 2 C, C-2), 20.1 (d, J
CP
= 38.1 Hz,
2 C, C-1) ppm.
31P-NMR (162 MHz, CDCl3, 300 K, H3PO4): 12.5 (s, 2P, PPh2·BH3) ppm.
11B-NMR (128 MHz, CDCl3, 300 K, BF3): -41.3 (s, 2 B, BH3) ppm.
7.7 N,N-Bis(2-(diphenylphosphaneyl)e hyl)-4- hiocyana oaniline-
bo ane-complex
DCM, 0 °C
N
Ph2PPPh2
BH3BH3
N
Ph2PPPh2
BH3BH3
SCN
NH4SCN
TBAB 3
10
11
104
7.7 N,N-Bis(2-(diphenylphosphaneyl)e hyl)-4- hiocyana oaniline-bo ane-complex
PN
Ph
P
Ph ·BH3
(10, 200 mg, 0.37 mmol) and ammonium hiocyana e (56.3 mg, 0.74) we e
dissol ed in a mix u e o DCM (5 mL) and me hanol (5 mL). In a second essel TBAB
3
(177 mg, 0.37 mmol) was dissol ed using he same mix u e. The ligand solu ion was cooled o
0°C and he TBAB
3
solu ion was added, changing he colo o a deep pu ple colo . A e
s i ing o 10 min, sodium hiocyana e solu ion (5 d ops) we e added. All ola ile componen s
we e emo ed in acuo and he c ude p oduc isola ed using die hyl e he . The p oduc was
ob ained as colo less solid.
Yield: 84.2 mg (0.14 mmol) 37 %
1
2
3
4
56
7
89
NP
P
10
11
BH3
BH3
SCN
12
1
H-NMR (400
MHz
,
CDCl3
, 300
K
):
δ
=7.68-7.61 (m, 8 H, H-9), 7.55-7.34 (m, 12 H,
H-10/H-11), 7.34-7.32 (m, 2 H, H-4), 7.19-7.15 (m, 2 H, H-5), 3.45-3.39 (m, 4 H, H-2),
2.44-2.36 (m, 4 H, H-1), 1.73-0.82 (m, 6 H, H-12) ppm.
13
C-NMR (100
MHz
,
CDCl3
, 300
K
):
δ
=147.7 (s, 1 C, C-3), 135.0 (s, 4 C, C-8), 132.2
(m, 2 C, C-4), 132.1 (s, 8 C, C-9), 131.8 (m, 8 C, C-10), 129.6 (s, 2 C, C-5), 129.2 (s, 4 C,
C-11), 129.6 (s, 1 C, C-6), 108.3 (s, 1 C, C-7), 45.3 (d, J
CP
= 5.80 Hz, 2 C, C-2), 23.4 (d,
JCP = 33.4 Hz, 2 C, C-1) ppm.
31P-NMR (162 MHz, CDCl3, 300 K, H3PO4): 12.5 (s, 2P, PPh2·BH3) ppm.
11B-NMR (128 MHz, CDCl3, 300 K, BF3): -41.3 (s, 2 B, BH3) ppm.
105

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Appendix
1
Suppo ing In o ma ion
Tungs en and Molybdenum Dini ogen Complex
Suppo ed by a Pen aden a e Te apodal
Phosphine Ligand: Compa a i e Spec oscopic,
Elec ochemical and Reac i i y S udies
Jannik Junge†a, S en F oi zheim†a, Tobias A. Engesse a, Jan K ahme a, Ch is ian Nä he a, Nicolas Le
Poul*b, Felix Tuczek*a
Con en page
[WCl3(κ3-P2MePP2Ph] 2
[W(N2)(P2MePP2Ph)] (2) 4
Elec ochemis y o [Mo(N2)(P2MePP2Ph)] (1) and [W(N2)(P2MePP2Ph)] (2) 12
1H-DOSY NMR spec um o [W(N2)(P2MePP2Ph)] (2) 13
[W(NNH2)(P2MePP2Ph)](BA F)2 (3-BA F) 14
[W(NNH2)(P2MePP2Ph)][Al(p b)4]2 (3-Al(p b)4) 24
Ca aly ic expe imen s 24
Ca esian coo dina es o [W(N2)(P2MePP2Ph)] (2) and [W(NNH2)(P2MePP2Ph)]2+ (3) 25
a.
Ins i u ü Ano ganische Chemie,
CAU Kiel, Max-Ey h-S . 2, 24118 Kiel.
Email: [email protected]
b.
Labo a oi e de Chimie, Élec ochimie Moléculai es e Chimie Analy ique (UMR CNRS 6521)
Uni e si é de B e agne Occiden ale, 6 A enue Le Go geu, 29238 B es , F ance
Email: Lepoul@uni -b es .
Elec onic Supplemen a y Ma e ial (ESI) o Dal on T ansac ions.
This jou nal is © The Royal Socie y o Chemis y 2022
121

Chap e 9 Appendix
2
[WCl3(κ3-P2MePP2Ph]
Figu e S1. X-band (9.8 GHz) EPR spec a o h solu ions o [WCl3(κ3-P2MePP2Ph] a oom
empe a u e (le ) and 77 K ( igh ). The X-band EPR spec a we e eco ded on a B uke EMX
Plus spec ome e wi h dual mode ca i y, 2.0 mW mic owa e powe and modula ion
ampli ude o 1 mT.
Figu e S2. IR and Raman spec um o [WCl3(κ3-P2MePP2Ph].
122
3
Table S1. Expe imen al equencies o he Raman and IR bands o [WCl3(κ3-P2MePP2Ph] [cm-1].
[WCl3(κ3-P2MePP2Ph] (2)
Raman
IR
Assignmen
Raman
IR
Assignmen
-
3067 (w)
-
-
945 (m)
CC
3054 (m)
3051 (w)
ν(CH)
-
917 (m)
CC
2982 (w)
-
νas(CH3/CH2)
-
880 (m)
-
-
2954 (sh)
-
-
843 (w)
-
2913 (s)
2919 (m)
νs(CH3/CH2)
-
805 ( w)
-
-
2867 (sh)
-
786 (w)
-
-
-
2801 (w)
-
-
739 (s)
-
1586 (s)
1589 (m)
CC
688 (w)
693 ( s)
-
1573 (w)
1568 (w)
-
-
639 ( w)
-
-
1551 ( w)
-
619 (w)
617 (w)
-
-
1480 (m)
-
-
577 ( w)
-
1455 ( w)
1455 ( w)
-
-
543 (w)
-
-
1430 (m)
PC
-
508 (s)
-
1414 (w)
1412 (w)
PC
-
479 (m)
-
-
1381 (w)
-
-
442 ( w)
-
-
1330 ( w)
-
-
425 (w)
-
1306 ( w)
1297 (w)
-
400 ( w)
404 ( w)
-
-
1279 (w)
-
-
362 ( w)
-
-
1260 ( w)
-
-
340 (sh)
-
-
1241 (w)
-
328 (w)
323 (sh)
-
1210 ( w)
-
-
-
294 (s)
-
1186 (w)
1182 (w)
-
-
271 ( s)
-
1160 (w)
1156 (w)
-
258 (w)
252 (sh)
-
-
1119 (w)
-
-
221 ( w)
-
1100 (w)
1096 (m)
-
-
208 ( w)
-
1073 ( w)
1069 (w)
-
-
178 (w)
-
1028 (m)
1025 (w)
-
150 ( w)
158 (w)
-
1000 ( s)
1000 (w)
CC
-
133 (m)
-
960 (w)
-
-
-
120 (w)
-
w = e y weak, w = weak, m = medium, s = s ong, s = e y s ong; ν = alence, δ = de o ma ion
123
Chap e 9 Appendix
4
[W(N2)(P2MePP2Ph)] (2)
NMR spec oscopy
Figu e S3. 1H NMR spec um o 2 in benzene-d6.
Figu e S4. Enla gemen o he alipha ic egion o he 1H NMR spec um o 2 in benzene-d6 and
assignmen o he signals.
124
5
Figu e S5. Enla gemen o he a oma ic egion o he 1H NMR spec um o 2 in benzene-d6.
Figu e S6. 13C NMR spec um o 2 in benzene-d6.
125
Chap e 9 Appendix
12
Supplemen a y elec ochemical and spec oelec ochemical da a o [W(N2)(P2MePP2Ph)] (2)
and [Mo(N2)(P2MePP2Ph)] (1).
Figu e S13. A) Plo o ipa(1) s. 1/2 om CV da a ob ained o [W(NNH2)(P2MePP2Ph)] (0.4 mM)
in THF/NaBPh4 20 mM, ed cu e: linea i ; B) CV o [Mo(N2)(PMe2PPPh2)] (1 mM) a P wo king
elec ode (diam. 1 mm) o = 05 V s-1 in THF/NaBPh4 20 mM.; C) In a ed spec a o
[W(N2)(PMe2PPPh2)] (15 mM) in THF/NaBPh4 20 mM eco ded du ing in-si u
spec oelec ochemical measu emen s be o e (black) and a e oxida ion a Epa(1) ( ed), hen
e u ning back o he ini ial po en ial (blue); (D) The same as (C) excep ha oxida ion a Epa(1)
( ed) is ollowed by oxida ion a Epa(2) (g een), hen back- educ ion o Epc(1) < E < Epa(2) (blue)
and inally Epc(1) (cyan).
132

13
1H-DOSY NMR expe imen o [W(N2)(P2MePP2Ph)] (2)
The 1H-DOSY NMR was measu ed wi h 13 mg (14.6 µmol) o [W(N2)(P2MePP2Ph)] (2) and 17 mg
(49.7 µmol) NaBPh4 in 0.5 ml deu e a ed THF. The esul ing alue o he di usion coe icien
was 9.5∙10-6 cm2 s-1.
Figu e S14. 1H-DOSY NMR spec um o [W(N2)(P2MePP2Ph)] (2).
133
Chap e 9 Appendix
14
Vib a ional spec oscopy o [W(NNH2)(P2MePP2Ph)](BA F)2 (3-BA F)
Figu e S15. a) IR and b) Raman spec a o (3-BA F) (black) and 15N2-3-BA F ( ed). The
enla gemen shows he N-H ib a ional equency and i s shi when labelling wi h 15N iso ope.
134
15
Table S7. Expe imen al equencies o he Raman and IR bands o
[W(NNH2)(P2MePP2Ph)](BA F)2 (3-BA F) [cm-1].
[W(NNH2)(P2MePP2Ph)](BA F)2 /
[W(15N15NH2)(P2MePP2Ph)](BA F)2
NaBA F
Assignmen
Raman
IR
Raman
IR
-
3312 (w) / 3308 (w)
-
-
N-H
3074 (w)
3076 ( w)
3084 (m)
-
ν(CH)
3023 ( w)
-
3029 (w)
-
νas(CH3/CH2)
2960 (w)
2960 (w)
-
2967 ( w)
-
2932 (m)
2924 (m)
-
-
νs(CH3/CH2)
2906 (m)
-
-
-
-
2882 (sh)
-
2885 (w)
-
-
2852 (w)
2853 (w)
-
-
-
-
-
2637 ( w)
2641 ( w)
-
-
-
2592 ( w)
-
-
-
-
2541 ( w)
-
-
-
1790 ( w)
-
-
-
-
-
-
1629 (w)
-
1611 (m)
1611 (m)
1611 (m)
1612 (m)
CC
1593 (s)
-
1596 (s)
-
CC
1523 ( w)
-
-
-
-
1464 (w)
-
1467 ( w)
-
-
-
1443 (w)
-
-
-
-
-
1422 ( w)
-
-
1364 (s)
1352 (s)
1367 (s)
1355 (s)
CF
-
-
1323 ( w)
-
-
-
1272 ( s)
1272 (w)
1277 ( s)
CC, CF
-
-
1197 (w)
1190 (sh)
-
-
1159 (m)
1161 (w)
1170 (m)
CC, CF
-
-
-
1139 (sh)
-
1107 (w)
1114 ( s)
1113 (w)
1115 ( s)
CC, CF
-
1092 (sh)
-
-
-
-
-
-
1063 (s)
-
1030 (w)
-
1043 (w)
-
-
1003 ( s)
998 (w)
1000 ( s)
1000 (w)
BC
135
Chap e 9 Appendix
16
-
-
-
964 (w)
-
952 (w)
-
-
-
-
939 ( w)
934 (w)
935 (w)
945 (m)
-
-
-
-
933 (m)
-
914 ( w)
918 ( w)
-
-
-
-
886 (s)
892 (w)
886 ( s)
CC
840 ( w)
838 (s)
837 ( w)
838 (s)
CC
-
809 (m)
-
-
-
801 (s)
-
801 (s)
-
CC
745 (w)
743 (m)
744 (m)
742 (m)
-
704 (s)
711 (s)
702 (s)
708 ( s)
CC
-
698 (w)
-
-
-
689 (w)
680 (s)
-
678 ( s)
CC
675 (w)
669 (s)
673 (m)
670 ( s)
-
617 ( w)
617 ( w)
-
-
-
-
609 ( w)
-
609 ( w)
-
-
580 (w)
583 (w)
582 (w)
-
-
568 ( w) / 554 (w)
-
-
W-N
-
516 (w)
-
-
-
-
507 (w)
-
505 ( w)
-
-
488 (w)
-
-
-
-
449 (m)
-
449 (m)
-
-
403 (w)
410 (m)
401 (w)
-
-
392 (w)
389 (w)
386 (w)
-
-
380 ( w)
-
-
-
-
366 (m)
-
366 (m)
CC, CF
-
353 (sh)
354 (w)
-
-
-
331 ( w)
-
-
-
-
-
321 (w)
317 ( w)
-
287 (w)
283 (w)
293 (m)
287 (w)
CC
262 (w)
259 (w)
261(w)
259 (w)
-
244 ( w)
246 ( w)
-
-
-
235 (w)
-
238 (s)
-
-
-
-
216 (w)
-
-
w = e y weak, w = weak, m = medium, s = s ong, s = e y s ong; ν = alence, δ = de o ma ion
136
17
[W(NNH2)(P2MePP2Ph)](BA F)2 (3-BA F)
NMR spec oscopy
Figu e S16. 1H NMR spec um o 3-BA F in die hyle he -d10.
Figu e S17. Enla gemen o he alipha ic egion o he 1H NMR spec um o 3-BA F in
die hyle he -d10 and assignmen o he signals.
137

Chap e 9 Appendix
18
Figu e S18. Enla gemen o he a oma ic egion o he 1H NMR spec um o 3-BA F in
die hyle he -d10 and assignmen o he signals
Figu e S19. 13C NMR spec um o 3-BA F in die hyle he -d10.
138
19
Figu e S20. Enla gemen o he alipha ic egion o he 13C NMR spec um o 3-BA F in
die hyle he -d10 and assignmen o he signals.
Figu e S21. Enla gemen o he a oma ic egion o he 13C NMR spec um o 3-BA F in
die hyle he -d10 and assignmen o he BA F-signals.
139
Chap e 9 Appendix
20
Figu e S22. Enla gemen o he a oma ic egion o he 13C NMR spec um o 3-BA F in
die hyle he -d10 and assignmen o he diphenylphosphine signals.
140
21
Figu e S23. 31P-31P-COSY spec um o 3- BA F in die hyle he -d10.
Figu e S24. 1H-31P-HMBC spec um o 3-BA F in die hyle he -d10.
141