Pu e
&
Appl.
Chem.,
Vol.
61,
No.
10,
pp.
1701-1706, 1989.
P in ed in G ea B i ain.
@
1989
IUPAC
Elec on- ich me al complexes o
C02
and
CS2
inco po a ion
E nes 0 Ca mona, Juan Cimpo a, Miguel A. MuRoz, Ma ga i a Paneque and
Manuel
L.
Po eda
Depa amen o de Quimica Ino ginica-Ins i u o de Ciencia de Ma e iales,
Facul ad de Quimica, Uni e sidad-CSIC, Apa ado 553,
41071
Se illa, Spain
Abs ac
-
The dihap o coo dina ion o wo molecules
o
ca bon dioxide o
a squa e-plana MoP2(P-P) agmen (P=monoden a e-, P-P=biden a e phosphi-
ne ligands) can occu in se e al ways gi ing ise o di e en con o me s.
Compounds o his ype ha e been p epa ed and hei spec oscopic p ope -
ies in es iga ed by a iable empe a u e 'H and 31P NMR s udies. The o -
ma ion o e hylene complexes ela ed o Mo(C2H4)2(PMe3)4,
6,
and he s udy
o hei eac i i y owa ds ca bon dioxide and ca bon disulphide is also
desc ibed. In pa icula , compound
6
induces a head- o- ail dime iza ion
o ca bon disulphide wi h o ma ion
o
a Mo(II)-C$4 linkage, which, in
he p esence o ca bon monoxide, unde goes
a
symme ic, oxida i e up u e,
which p oduces a Mo(0) complex and wo molecules o ca bon disulphide. The
inse ion eac ions
o
ca bon dioxide and o he unsa u a ed molecules in o
he nickel-ca bon bonds
o
he nickelacyclopen ene complexes
9
ha e been
in es iga ed and di e en o ganic p oduc s isola ed by means o simple o
sequen ial inse ion eac ions.
INTRODUCTION
The eac ions o ca bon dioxide wi h ansi ion me al complexes ha e been ex ensi ely in es-
iga ed in he las decade. These in es iga ions ha e led o he isola ion o some s able
ansi ion me al-ca bon dioxide complexes, as well as o he obse a ion o ca bon-ca bon
coupling eac ions be ween ca bon dioxide and a a ie y o o ganic subs a es ( e s.
1-5).
Conside able p og ess has been made in he unde s anding o he in e ac ion o ca bon dioxide
wi h ansi ion me als bu many impo an aspec s o his chemis y emain li le explo ed o
unde de eloped,
so
ha ca bon dioxide chemis y is s ill a p omising a ea o esea ch.
In o de o o e come he di icul ies e y o en encoun e ed in he s udy o he eac ions o
ca bon dioxide wi h ansi ion me als, ca bon disulphide and o he ela ed molecules ( e .
6)
ha e been used as models o ca bon dioxide chemis y. Howe e , he esul s ob ained o da e
clea ly show ha hese molecules exhibi a e y dis inc chemical beha iou which only e y
a ely pa allels ca bon dioxide chemis y. In pa icula , ca bon disulphide displays a e y
ich chemis y o much in insic academic in e es . In his con ibu ion we wish o epo
some eac ions o ca bon dioxide wi h complexes o molybdenum and nickel, ha lead o adduc
o ma ion o o inse ion in o a me al-ca bon bond. The eac ions o hese complexes wi h CS2
a e also desc ibed.
CARBON DIOXIDE AND CARBON DISULPHIDE COMPLEXES
OF
MOLYBDENUM
Ca bon dioxide complexes con aining chela ing phosphine ligands
Coo dina ion o ca bon dioxide in i s in ac o m o a ansi ion me al is a a e esul and
he numbe o s uc u ally cha ac e ized complexes is he e o e e y limi ed. A a iance
wi h he beha iou ound o o he ca bon dioxide complexes, he bis-ca bon dioxide adduc
ans-Mo(C02)2(PMe3)4,
(l),
has been epo ed o unde go a acile subs i u ion o one o he
coo dina ed PMe3 g oups by an isocyanide ligand, wi h o ma ion o
uns,me -Mo(C02)2(CNR)(P
Me3)3
emp s o subs i u e a second phosphine by hea ing a 5O-6O0C, in he p esence o an excess
o he isocyanide, lead o
loss
o
ca bon dioxide. We ha e now ound ( e .
8)
ha chela ing
diphosphine ligands e ec subs i u ion o wo molecules
o
ime hylphosphine o complex
1,
wi hou change in he coo dina ion mode o he ca bon dioxide g oups. Compounds,Za-Zb,
a e
o med, as shown in eac ion
(1).
The new complexes a e yellow c ys alline solids which dis-
play
IR
and NMR spec oscopic p ope ies e y simila o hose epo ed o he pa en com-
pound
1.
Ou in e es in complexes
2
was mainly concen a ed in he ollowing poin s:
i)
assuming ha he coo dina ed C02 ligands a e s agge ed wi h espec o one ano he and
( e ,
7).
Subs i u ion o he ca bon dioxide ligands is no obse ed, al hough a -
1701
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1702
E.
CARMONA
e a/.
eclipsing he
P-Mo-P
ec o s o he equa o ial plane, as p edic ed heo e ically o
1
( e .
9)
and demons a ed by X- ay s udies o he mono-isocyanide de i a i e ( e .
7),
he e could
be h ee di e en con o ma ions in compounds
2,
as ep esen ed in s uc u es
3-5.
Would any
3
4
5
o hese con o ma ions be a ou ed in solu ion and in he solid s a e?,
ii) compounds
2,
as he pa en complex
1,
a e luxional, and he p ocess esponsible o he
obse ed changes in he
NMR
spec a is o a ion a ound he molybdenum-ca bon dioxide bond
axis. Since he e a e wo molecules o ca bon dioxide coo dina ed o he molybdenum a om, he
ques ion a ises as o wha is he na u e o he o a ion p ocess.
Va iable empe a u e
NMR
s udies p o ide some clues o bo h ques ions. The oom empe a u e
31P{1H1 NMR
o complex
2a,
consis s o wo e y b oad and ea u eless humps, which gi e no
use ul in o ma ion wi h ega ds o he s uc u e o he compound. Upon cooling some changes
a e obse ed, and a
-9OOC
ou di e en se s o esonances
(AMNX
spin sys em) appea . This
is in acco d wi h s uc u e
2
and no wi h
2
o
4.
Wi h espec o he second o he abo e
ques ions, namely he na u e o he luxional p ocess, a clea dis inc ion be ween he possi-
ble mechanisms canno be achie ed wi h p esen da a. In he low empe a u e limi
(-75OC)
he
'H NMR
spec um o
2a
consis s o wo pa ially supe imposed double s o he
PMe3
ligands,
as well as o ou double s, one o each o he dmpm me hyl g oups, in acco d wi h he igid
s uc u e
5
p oposed o hese complexes. Upon wa ming he spec um simpli ies and a
4OoC
i
consis s o one double o he ime hylphosphine g oups and wo
double s
o
he me hyl
p o ons o he chela ing phosphine ligand, in ag eemen wi h a conce ed, bu no wi h a an-
dom o a ion. Finally, in acco d wi h hese obse a ions, he
31P{1H1 NMR
spec um o com-
pounds
2
consis s, a high empe a u es
(60-80°C),
o a pa e n o lines cha ac e is ic o an
AA'XX' spin sys em ( e .
8).
Wi h he aim o ob aining new ca bon dioxide complexes, he eac ions o a ious dini ogen
complexes o molybdenum, p epa ed as summa ized in eac ions
(2)-(4),
wi h
C02
ha e been s u-
"Mo(N2 )3(PE~3
)3"
+
PME~
-
=-Mo(
N2
)2
(PME~)
3(
PET^)
+
died. Reac ion
(3)
p oduces in ac
a
mix u e o he is-dini ogen complex and he dini o-
gen b idged species
[Mo(N2)2(PE 3)2]2(~-N2),
w i en in a simpli ied o m as shown. Ac ion o
C02
upon solu ions o hese complexes p o ide only ca bona e complexes, i. e., he p oduc s
o he so-called educ i e disp opo iona ion o ca bon dioxide, and he e o e hei in es i-
ga ion has no been pu sued any u he ( e .
10).
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Elec on ich me al complexes o
CO,
and
CS,
inco po a ion
1703
Reac ions
o
anaM~(C~H~)~(PMe~)~,
(61,
and ela ed complexes wi h ca bon dioxide and
ca bon disulphide
We ha e ecen ly epo ed ha ca bon dioxide eac s wi h one o he coo dina ed e hylene
li-
gands o complex
6,
o ming a new C-C bond ( e .
11).
The p oduc o his eac ion is a binu-
clea molybdenum complex which con ains wo b idging ac yla e ligands ( e . 12), and he a-
P
cile ac i a ion o ca bon dioxide by complex
6
is p obably a consequence o he elec on- ich
na u e o he me al cen e and o he a ailabili y o a acan coo dina ion posi ion by aci-
le dissocia ion o one o he ime hylphosphine ligands ( e .
11).
In o de o gain u he
in o ma ion on his ema kable ans o ma ion o he ela ed sys ems ha e been in es iga ed,
eac ions
(5)-(7):
P-P=
DMPM, DMPE
i) a emp s o p epa e he p opylene analogue o
6
lead ins ead o a hyd ido ally1 species
( e . 13) which eac s wi h ca bon dioxide wi h e olu ion o p opylene and o ma ion o
1
and
o he p oduc s ( e .
10).
ii) PMe3 subs i u ion in
6
by he Il-acid ligands
CO
o CNR ( e . 14) a o ds new e hylene com-
plexes as ep esen ed in eac ion
(6).
No unexpec edly, hei eac i i y owa ds ca bon dio-
xide does no pa allel ha o
6.
iii) compounds ela ed o
6
con aining chela ing phosphine ligands can be p epa ed as depic-
ed in equa ion (7). These compounds a e su p isingly ine owa ds ca bon dioxide. Fo ins-
ance, he dmpe de i a i e can be eco e ed unchanged a e hea ing a 6OoC, o se e al ho-
u s, in e ahyd o u an, unde 2-3 a m o ca bon dioxide. The lack o eac i i y in his case
e lec s p obably he non a ailabili y o a acan coo dina ion posi ion.
I was also o in e es o asce ain i o he he e ocumulenes, in pa icula ca bon disulphi-
de, would unde go simila ans o ma ions. Addi ion
o
ca bon disulphide o solu ions o com-
plex
6
p oduces a black solid o composi ion Mo(C~S,)(C,H,)(PM~~)~,
(7),
which has he PMe3
g oups in a me idional dis ibu ion. The e hylene ligand
anysoch onous me hylenic p o ons, while he wo CS2 molecules gi e ise o a single and a
qua e (I3C en iched sample o
7,
227
and
293
ppm, espec i ely), sugges ing ha one o he
ca bon disulphide g oups is C-bonded o he me al a om. The bonding mode o he C2S4 uni has
been de e mined by X- ay s udies ( e .
15)
which show he wo molecules o CS2 ha e linked o
a head- o- ail dime . Fo ma ion o
7
can he e o e be ep esen ed as in equa ion
(8).
has equi alen CH2 moie ies bu
7
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1704
E.
CARMONA
e a/.
Me allocyclic complexes o his ype a e o en p oposed as in e media es in he me al-p omo-
ed educ i e disp opo iona ion o ca bon dioxide and ela ed molecules, al hough conclusi e
e idence has ne e been ob ained ( e .
16).
Fu he mo e, he e is a su p ising lack o s u-
dies aimed a he in es iga ion o he chemical eac i i y o hese uni s. Compound
7
exhi-
bi s a high he mal s abili y and does no decompose,
no p oduces he disp opo iona ion p o-
duc s, CS and CS32-, a e hea ing a 120°C o se e al hou s. An unexpec ed eac ion occu s
wi h ca bon monoxide unde ela i ely mild condi ions (5OoC,
2
a m).
As
shown in Scheme
I,
symme ic oxida i e up u e o he C2S4 uni is obse ed, wi h educ ion o he molybdenum(0)
complex
8,
i.
e., he e e se o he educ i e di ne iza ion eac ion. These esul s no only
demons a e a new ype
o
eac i i y o hese me alacyclic uni s,
bu ques ion hei p oposed
in e mediacy in he ansi ion me al induced educ i e disp opo iona ion o he e ocumulenes.
INSERTION CHEMISTRY
OF
THE
NICKELACYCLOPENTENE COMPLEX
Ni[CH2C(Me)2-O-C6H41(PMeJ)2
9a.
REACTIONS WITH CARBON DIOXIDE,
CARBON DlSULPHlDE AND OTHER UNSATURATED MOLECULES
The nickelacyclopen ene complex
9a
has a ich inse ion chemis y and eac s wi h ca bon mo-
noxide, ca bon dioxide, ca bon disulphide and o he unsa u a ed molecules ( e .
17)
wi h o -
ma ion o a a ie y o o ganic and me allo-o ganic p oduc s.
The in e ac ion o
9a
wi h CO and PhCaCPh, unde ambien condi ions, akes place as indica ed
in equa ions
(9)
and
(10).
As shown, inse ion is ollowed by a apid educ i e elimina ion
which yields he co esponding o ganic and me allo-o ganic p oduc s.
A
di e en ia ion be ween he wo possible eac ion pa hways, namely inse ion in o he ni-
ckel-alkyl
o
a yl ca bon bonds, can be accomplished by ca ying ou , in ei he o de , he
sequen ial inse ions depic ed in eac ion
(11)
( e .
18).
Fo ma ion o
10
unequi ocally
s ablishes ha he inse ion o CO akes place exclusi ely in o he nickel-ca bon alkyl bond.
9a
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Elec on ich me al complexes o
CO,
and
CS,
inco po a ion
1705
In he p esence o we C02, compound
9a
unde goes a as p o oly ic clea age o he nickel-
-a yl bond, wi h o ma ion o he binuclea , ca bona e-b idged species
11,
eac ion
(12).
In
he absence o wa e , he nickelalac one de i a i e
12
is
o med as he esul
o
he inse -
P
PHCME CH
0
I
2 N~’ ‘C-O-N!-CH~C~~PH
I
(12)
P
Y
p/
O’
11
(13)
NI
9a
P’
o-c
II
12
0
ion o ca bon dioxide in o he Ni-a yl bond ( eac ion 13). The exis ence in hese compounds
o Ni-C bonds, sugges u he inse ion chemis y can be pu sued, and indeed, in e ac ion
wi h ca bon monoxide (20°C,
1
a m) p oceeds as indica ed in eac ions (14) and
(15).
While
he o me dese es no addi ional commen s, he esul s o he la e eac ion a e a he
unexpec ed, ( e .
17)
since hey co espond, in a o mal sense, o a me al p omo ed oxida i e
conp opo iona ion o ca bona e and ca bonyl ligands. Two molecules o ca bon dioxide a e
o med, one o hem is e ol ed as ee C02 and he o he becomes inco po a ed in o he anhy-
d ide unc ionali y.
The eac ion o
9a
wi h 3-4 equi o ca bon disulphide ( e .
19)
p oduces a ed-b own mic o-
c ys alline p ecipi a e o he known complex
13
( e .
20),
oge he wi h a ed solu ion,
om which ed c ys als o he di hiolac one
14
can be isola ed (Scheme
11).
The na u e o
13
and
14
implies he in e mediacy o a Ni(0) species,
15,
which can, in ac , be isola ed by
he low empe a u e eac ion o
9a
wi h a sligh de ec
o
ca bon disulphide.
As
expec ed,
15
eac s wi h excess CS2, wi h o ma ion
o
13
and
14.
I seems likely, ha he i s s ep
in his eac ion is inse ion o ca bon disulphide in o he nickel-a yl ca bon bond, and his
has been con i med, as al eady indica ed, by isola ion o complex
10,
as he esul o he
sequen ial inse ion o ca bon disulphide and ca bon monoxide (see eac ion
11).
The esul-
ing nickeladi hiolac one in e media e species, which would in ac be he CS2 analogue
o
12,
unde goes educ i e elimina ion, wi h concomi an in amolecula C-S bond o ma ion, o
yield he obse ed complex
15.
Scheme
I/
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1706
E.
CARMONA
e a/.
A
e y di e en eac ion is obse ed be ween ca bon disulphide and complex
9b,
he dmpe
analogue o
9a.
Upon addi ion o
2
equi o ca bon disulphide o a solu ion
o
9b,
he
i hioca bona e
16
and he hioke ene
17
a e o med (Scheme
111).
This eac ion co esponds
o mally o a me al-induced educ i e disp opo iona ion o ca bon disulphide bu , a he
in e es ingly, i occu s wi hou change in he oxida ion s a e o he me al cen e. Ac ion o
1
equi o ca bon disulphide upon compound
9b
a o ds he 1,l-di hiola e species
18,
which,
as expec ed, eac s wi h ano he equi alen o ca bon disulphide, wi h o ma ion o
16
and
17.
Thus, he cou se o he eac ion o ca bon disulphide wi h he nickelacyclopen ene de i a i-
es
9
depends ma kedely on he na u e o he phosphine co-ligands. I seems easonable ha
he eac ion o
9b
wi h ca bon disulphide p oceeds also wi h ini ial inse ion o he he e o-
cumulene in o he nickel-a yl bond. The chela ing na u e o he dmpe ligand p e en s phosphi-
Scheme
Ill
2
cs2
9b
ne dissocia ion and may induce C-C ins ead o C-S bond o ma ion. Ne e heless, elec onic
ac o s mus also play an impo an ole and his is clea ly mani es ed by he cou se o he
eac ion o he 2,2'-bipy idine de i a i e
9c
( e .
18)
wi h ca bon disulphide. As shown in
equa ion
(16),
his yields a complex con aining he coo dina ed di hiolac one
14,
ha is, a
p oduc analogous o he ime hylphosphine de i a i e
15.
No e idence o he o ma ion o a
1.1-di hiola e complex analogous o
18
has been ound.
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19
*
20.
9c
Acknowledgemen
1.
The au ho s g a e ully acknowledge he con inuous suppo o he Minis e io de
Educaci6n
y
Ciencia and he Agencia Nacional de E aluaci6n
y
P ospec i a.
We hank P o esso Pie e B auns ein o a p e-p in o e e ence
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