Metal nanoparticles (Fe, Co, Ni, Ru) stabilised by SNS and NHC ligands. Synthesis, Characterisation and Catalytic Applications

i! C S IC
C ONSE J O SUPERIOR DE INVESTIGACIONES C IENT F ICA S
Me al nanopa icles (Fe, Co, Ni, Ru)
s abilised by SNS and NHC ligands.
Syn hesis, Cha ac e isa ion and
Ca aly ic Applica ions
PABLO MOLINILLO FERNÁNDEZ
SEVILLA 2024
INSTITUTO DE INVESTIGACIONES QUÍMICAS
Tesis Doc o al
Me al nanopa icles (Fe, Co, Ni, Ru) s abilised by
SNS and NHC ligands. Syn hesis, Cha ac e isa ion
and Ca aly ic Applica ions.
Pablo Molinillo Fe nández
Se illa, 2024
Me al nanopa icles (Fe, Co, Ni, Ru) s abilised by
SNS and NHC ligands. Syn hesis, Cha ac e isa ion
and Ca aly ic Applica ions.
po
Pablo Molinillo Fe nández
Memo ia p esen ada pa a op a al
Tí ulo de Doc o en Química
MOLINILLO
Fi mado digi almen e po
MOLINILLO FERNANDEZ
FERNANDEZ PABLO
PABLO -
-
Fecha: 2024.12.04
10:35:06 +01'00'
Fdo. Pablo Molinillo Fe nández
LARA
MUÑOZ
PATRICIA -
Fi mado
digi almen e po
LARA MUÑOZ
PATRICIA –
Fecha: 2024.12.04
10:32:29 +01'00'
Di ec o as
RENDON
MARQUIEZ
NURIA -
Fi mado
digi almen e po
RENDON MARQUIEZ
NURIA
–
Fecha: 2024.12.04
10:30:13 +01'00'
Pa icia La a Muñoz Nu ia Rendón Má quez
P o eso a Ti ula de la P o eso a Ti ula de la
Uni e sidad de Se illa Uni e sidad de Se illa

A mi amilia.
A quien ya es pa e de ella,
y a quien llegue en el u u o.
I
Table o con en s
Acknowledgmen s ..................................................................................................... III
Lis o abb e ia ions ................................................................................................... V
Conside aciones gene ales ...................................................................................... VII
Chap e I: Gene al In oduc ion .................................................................................. 1
Chap e II: Objec i es ............................................................................................... 53
Chap e III: Reduc ion o N2O wi h hyd osilanes ca alysed by Ru∙SNS NPs ........... 57
Chap e IV: 1s ow ansi ion me al NPs s abilised by NHC ligands as ca alys s o
he me hanolysis o ammonia-bo ane ................................................................. 103
Chap e V: Ru and Ni∙MIC NPs as ca alys s o chemoselec i e H/D exchange on
hyd ides o main g oup elemen s ........................................................................ 159
Chap e VI: Conclusions ......................................................................................... 223
VIII
El Capí ulo III desc ibe la sín esis y ca ac e ización de nanopa ículas de
u enio es abilizadas median e ligandos de ipo SNS (azu e-ni ógeno-azu e), así
como su aplicación ca alí ica en la educción de óxido ni oso median e silanos. Es e
capí ulo se encuen a a su ez di idido en es secciones. En la p ime a se ealiza una
b e e in oducción al sis ema es udiado, especi icando la aplicación ca alí ica que se
abo da á pos e io men e. En la segunda sección se desa ollan y discu en los
esul ados ob enidos, an o en elación con la sín esis de los ligandos y nanopa ículas
mencionados, como con el p ocedimien o ca alí ico es udiado. Finalmen e, en la
e ce a sección se desc iben los aspec os expe imen ales, incluyendo las écnicas
empleadas y los p o ocolos seguidos en cada caso.
De mane a simila , el Capí ulo IV es á dedicado al es udio de nanopa ículas
basadas en me ales de la p ime a se ie de ansición, conc e amen e hie o, cobal o y
níquel, es abilizadas median e ligandos de ipo NHC (Ca benos N-He e ocíclicos),
que se han empleado como ca alizado es en la ob ención de hid ógeno median e
me anólisis del aduc o de bo ano del amoniaco. La p ime a sección de es e capí ulo
consis e en una b e e in oducción al campo, especi icando los dis in os
p ocedimien os de ob ención de hid ógeno. La segunda sección desc ibe el p oceso
de sín esis y ca ac e ización de las mencionadas nanopa ículas de hie o, cobal o y
níquel, así como las di e en es p uebas ca alí icas ealizadas. Finalmen e, la e ce a
sección explica el p ocedimien o expe imen al seguido en cada caso.
El Capí ulo V a a la sín esis y ca ac e ización de nanopa ículas an o de
u enio como de níquel, es abilizadas po ligandos de ipo MIC (Ca benos
Mesoiónicos), así como su aplicación ca alí ica en la deu e ación de hid osilanos y
o os hid u os de elemen os de los g upos p incipales (Ge, Sn, B). Siguiendo la misma
es uc u a desc i a pa a los capí ulos an e io es, en la p ime a sección se in oduce el
sis ema, ealizando un b e e epaso de los p ocesos de in e cambio iso ópico desc i os
en la bibliog a ía. En la segunda sección se discu en los esul ados ob enidos en la
p epa ación y e aluación del compo amien o ca alí ico de las nanopa ículas de
u enio y las de níquel. Finalmen e, en la e ce a sección se especi ican los
p ocedimien os expe imen ales empleados.

IX
Po úl imo, el Capí ulo VI ecopila las p incipales conclusiones de i adas de
la in es igación lle ada a cabo en es e abajo.
Con la inalidad de op a a la Mención In e nacional en el í ulo de Doc o
(RD 99/2011; a ículo 15), la p esen e Tesis Doc o al, con excepción de es as
Conside aciones Gene ales, se ha edac ado en inglés. Además, como equisi o
imp escindible pa a op a a dicha Mención, se ealizó en el año 2023 una es ancia de
es meses en el g upo de in es igación de la D a. Ka ine Philippo , pe enecien e al
“Labo a oi e de Chimie de Coo dina ion-Cen e Na ional de la Reche che
Scien i ique” (LCC-CNRS) en Toulouse, F ancia. Es a es ancia se inanció a a és
del p og ama iMOVE del Consejo Supe io de In es igaciones Cien í icas y ue
supe isada po la D a. Nu ia Rome o, Maî e de con é ences de la Uni e sidad
Toulouse III-Paul Saba ie , e in es igado a de dicho g upo. La in es igación lle ada
a cabo du an e la es ancia se enma ca en la u ilización de nanopa ículas de me ales
de la p ime a se ie de ansición en p ocesos elec oca alí icos de Wa e Spli ing. Las
nanopa ículas u ilizadas como elec oca alizado es son las desc i as en el Capí ulo IV
de la p esen e Tesis Doc o al. Los esul ados de elec oca álisis se encuen an
ac ualmen e en p oceso de análisis y no han sido incluidos en es a memo ia.
Las igu as, ablas, esquemas y e e encias bibliog á icas se encuen an
enume adas de o ma independien e pa a cada capí ulo. Cada una de las uen es
consul adas se encuen an especi icadas como no as a pie de página la p ime a ez
que son u ilizadas en un capí ulo de e minado y, de mane a adicional, al inal de cada
capí ulo.
El análisis median e Espec oscopía Fo oelec ónica de ayos X (XPS)
incluido en los Capí ulos III, IV y V de es a memo ia ha sido lle ado a cabo po la
D a. Flo encia Va ie Laga igue del Ins i u o de Ciencia de Ma e iales de Se illa
(ICMS) y P o eso a Asociada del Depa amen o de Química Ino gánica de la
Uni e sidad de Se illa. De mane a simila , la ob ención y pos e io a amien o de las
imágenes de Mic oscopía Elec ónica de T ansmisión de Al a Resolución (HRTEM)
p esen adas en los Capí ulos III y V han sido ealizados po el D . Be and Lac oix,
X
del g upo T ibología y P o ección de Supe icies del Depa amen o de Física Aplicada
I de la Uni e sidad de Se illa, y po la D a. Ana Bel án Cus odio, P o eso a Ti ula
del Depa amen o de Ingenie ía y Ciencia de los Ma e iales y del T anspo e de la
Uni e sidad de Se illa. Las imágenes análogas p esen adas en el Capí ulo IV han sido
ealizadas po Vincen Colliè e, esponsable del Se icio de Mic oscopía Elec ónica
del “Labo a oi e de Chimie de Coo dina ion” de Toulouse, F ancia.
Pa e de los esul ados ob enidos du an e la ealización de es a Tesis Doc o al
han sido publicados en e is as cien í icas del ámbi o de la Química, y
especí icamen e de la Nanociencia y la Ca álisis. Además, al menos dos a ículos se
encuen an en p oceso de edacción. Los a ículos ya publicados se indican a
con inuación:
Reduc ion o N2O wi h hyd osilanes ca alysed by RuSNS nanopa icles. Pablo
Molinillo, Be and Lac oix, Flo encia Va ie , Nu ia Rendón, And és Suá ez, Pa icia
La a, Chem. Commun., 2022, 58, 7176-7179. DOI: 10.1039/d2cc01470j.
Ru henium nanopa icles s abilized by 1,2,3- iazolylidene ligands in he
hyd ogen iso ope exchange o E-H bonds (E = B, Si, Ge, Sn) using deu e ium gas.
Pablo Molinillo, Maxime Puyo, Flo encia Va ie , Be and Lac oix, Nu ia Rendón,
Pa icia La a, And és Suá ez. Nanoscale, 2023, 15, 14488-14495. DOI:
10.1039/d3n 02637j.
Chap e I:
Gene al In oduc ion
Chap e I o his PhD hesis se es as a gene al in oduc ion o he undamen al
concep s o nanoscience and nano echnology, wi h a ocus on he s udy o
nanopa icles. I co e s aspec s such as hei classi ica ion, syn hesis,
cha ac e isa ion and applica ions, pa icula ly in he ield o ca alysis.
Gene al In oduc ion
3
Table o Con en s
1.1 Nanoscience and nano echnology ......................................................................... 5
1.2 Nanopa icles. Gene al aspec s ............................................................................. 8
1.2.1 O ganic nanopa icles .................................................................................... 9
1.2.2 Ca bon-based nanopa icles ......................................................................... 10
1.2.3 Ino ganic nanopa icles ................................................................................ 12
1.3 Syn hesis o me al nanopa icles ......................................................................... 13
1.3.1 Fo ma ion mechanism .................................................................................. 13
1.3.2 Top-down and bo om up me hodologies ..................................................... 16
1.3.3 O ganome allic app oach in nanopa icle syn hesis ..................................... 18
1.4 S abilisa ion o nanopa icles .............................................................................. 21
1.4.1 Elec os a ic s abilisa ion ............................................................................. 22
1.4.2 S e ic s abilisa ion ........................................................................................ 22
1.4.3 Elec os e ic s abilisa ion ............................................................................. 23
1.4.4 S abilisa ion by solid suppo s ..................................................................... 23
1.4.5 S abilisa ion by ligands. ............................................................................... 23
1.5 Cha ac e isa ion o me al nanopa icles .............................................................. 33
1.5.1 T ansmission Elec on Mic oscopy (TEM and HRTEM) ............................... 33
1.5.2 Scanning T ansmission Elec on Mic oscopy (STEM)................................ 34
1.5.3 Induc i ely Coupled Plasma (ICP) ............................................................... 34
1.5.4 X- ay Pho oelec on Spec oscopy (XPS) .................................................... 35
1.6 Ca alysis by me al nanopa icles ......................................................................... 35
1.7 Re e ences ........................................................................................................... 43

Gene al In oduc ion
5
1.1 Nanoscience and nano echnology
The mode n concep o nanoscience was in oduced in 1959 du ing Richa d
Feynman’s lec u e “The e’s Plen y o Room a he Bo om” p esen ed a he annual
mee ing o he Ame ican Physical Socie y a Cal ech (Cali o nia Ins i u e o
Technology).1 In his lec u e, he au ho p oposed a ious me hods and ool se s o
ans o m indi idual a oms o molecules in o nanoscale ma e ials, including he
possibili y o building machines a a molecula le el o e en smalle . Due o hese
g oundb eaking ideas, he is ega ded as he a he o nano echnology. A decade and a
hal la e , in 1974, he e m o nano echnology was coined by No io Taniguchi,
discussing he concep in he con ex o ma e ials p ocessing. He s a ed ha
“nano echnology mainly consis s o he p ocessing o sepa a ion, consolida ion and
de o ma ion o ma e ials by one a om o one molecule”.2
Nowadays, i is widely accep ed ha nanoscience in ol es he s udy o
s uc u es and molecules a he nanome e scale, ypically de ined as anging om 1
o 100 nanome es (1 nm = 10-9 m).3 Nano echnology, in u n, ocuses on he
de elopmen o p ac ical applica ions o nanoscience. In ha sense, nanoscience is
en isaged as a mul idisciplina y discipline ha co e s he a eas o physics, chemis y,
biology, medicine and ma e ial science. I enables he s udy o unp eceden ed
phenomena occu ing a he a omic and molecula le el, while nano echnology is
p ima ily conce ned wi h he con olled assembly o nanoma e ials. The impo ance
o nano echnology lies in he ac ha in he nanome ic size, ma e ials exhibi
di e en p ope ies compa ed o hei mac oscopic coun e pa s. Nanoma e ials, wi h
small size and high su ace o olume a io, exhibi excep ional physical (op ical,
elec ical, mechanical and magne ic) and chemical p ope ies (such as ca aly ic
1 R. P. Feynman, “The e’s Plen y o Room a he Bo om”, Enginee ing and Science 1960, 23,
22-36.
2 N. Taniguchi, C. A akawa, T. Kobayashi, “On he basic concep o nano- echnology”,
P oceedings o he In e na ional Con e ence on P oduc ion Enginee ing, Tokyo, Japan, 26-29
Augus 1974.
3 S. Bayda, M. Adeel, T. Tuccina di, M. Co dani, F. Rizzolio, Molecules 2020, 25, 112-126.
Chap e I
6
ac i i y).4 These p ope ies can be p ecisely uned by con olling he size, shape,
syn hesis condi ions, and app op ia e unc ionalisa ion o he nanoma e ials.
Nanoma e ials ha e been used o cen u ies. His o ical examples o
nanoma e ial use can be ound in a ious ancien ci iliza ions, wi h he Lycu gus cup
being one o he mos amous cases (Figu e 1). This Roman chalice demons a es he
unique op ical p ope ies o gold and sil e nanopa icles. Unde e lec ed ligh , i
exhibi s a pea-g een colou , while illumina ion wi h ansmi ed ligh , e eals a ed-
wine hue.5
Figu e 1. The Lycu gus Cup, B i ish Museum. Image used unde non-comme cial
C ea i e Commons (CC BY-NC-SA 4.0) license.
In he las ew decades, nanoscience has a ac ed he a en ion o he scien i ic
communi y and, subsequen ly, ecen ad ances in p epa a ion and cha ac e isa ion o
nanoma e ials ha e p oduced a boom in science and indus y, con ibu ing o nea ly
e e y ield o science and echnology, including human heal h, compu e science, and
ca alys s de elopmen . The la e will be explo ed in dep h in ollowing sec ions.3,6,7
Nanoma e ials, which a e key elemen s o nano echnology, exhibi a leas one
4 N. Baig, I. Kammakakam, W. Fala h, Ma e . Ad . 2021, 2, 1821-1871.
5 D. J. Ba be , I. C. F ees one, A chaeome y 1990 32, 33-45.
6 S. P. Fo s e , S. Ol ei a, S. Seege , In . J. Nano echnol. 2011, 8, 592-612.
7 M. R. Axe , K. Philippo in Nanopa icles in Ca alysis: Ad ances in Syn hesis and
Applica ions, Chap e 4, 73-97, K. Philippo , A. Roucoux (Eds), Wiley-VCH, 2021.
7
Gene al In oduc ion
dimension measu ing be ween 1 and 100 nm, and can be classi ied based on a ious
c i e ia, including hei dimensions, shape, and s uc u e. In e ms o he numbe o
dimensions on he nanoscale, nanoma e ials can be classi ied in o ou ca ego ies, as
ep esen ed in Figu e 2.8,9
Figu e 2. Nanoma e ials classi ied in 0D, 1D, 2D and 3D ca ego ies.
Ze o-Dimension nanoma e ials (0D): These nanoma e ials possess all dimensions a
he nanoscale. Classical examples include nanopa icles, ulle enes, and quan um
do s.8
One-Dimension nanoma e ials (1D): Nanoma e ials in his ca ego y ha e wo
nanoscale dimensions and he hi d one in he mic oscale. They include s uc u es
such as nano ibe s, nano ubes, nano ods, and nanowi es.10
Two-Dimension nanoma e ials (2D): These nanoma e ials ha e only one dimension
in he nanoscale. G aphene is pe haps he mos ep esen a i e example in his
ca ego y, which also includes ma e ials like nanoshee s o nanolaye s.11,12
8 N. Joudeh, D. Linke, Jou nal o Nanobio echnology 2022, 20, 262.
9 J-H. Son, Y-U. Kwon, Bull. Ko ean. Chem. Soc 2001, 22, 1224-1230.
10 J. J. Ramsden in Nano echnology: An In oduc ion, Chap e 6, 101-124, J. J. Ramsden (Ed),
William And ew Publishing, 2011.
11 P. Feng, Y. Kong, M. Liu, S. Peng, C. Shuai, Ma e ials Today Nano 2021, 15, 100127.
12 T. Imae in Nanolaye Resea ch: Me hodology and echnology o g een chemis y, Chap e
1, 1-34, T. Imae (Ed), Else ie , 2017.
Chap e I
14
In s age I, he concen a ion o monome inc eases o e ime because o he me al
p ecu so decomposi ion un il he solu ion becomes sa u a ed, and eaches he
supe sa u a ion concen a ion (Cmin). A his poin , indi idual a oms s a o agg ega e
homogeneously, bu no nanopa icles a e p esen in suspension. In s age II, he
monome concen a ion exceeds he supe sa u a ion le el, igge ing he nuclea ion o
nanopa icles and a co esponding dec ease in he monome concen a ion o alues
below Cmin. F om s age III onwa d, no new pa icle nuclea ion occu s, only he g ow h
o exis ing nanopa icles con inues un il he p ecu so is exhaus ed. In his con ex ,
he maximum pa icle size is de e mined by he amoun o p ecu so employed and
he numbe o nuclei gene a ed in s age II. The LaMe mechanism is used o explain
eac ions ha ake place in closed sys ems, whe e he numbe o nanopa icles o med
s ongly depends on he nuclea ion p ocess. Typically, nanopa icles ha ollow he
LaMe mechanism p esen a wide size dis ibu ion due o he complex nuclea ion and
g ow h s eps, whe e he coalescence o wo nuclei can lead o a loss o monodispe si y.
In ecen yea s, a modi ica ion o he o iginal LaMe mechanism has been p oposed
by Hube e al., ep esen ed in Figu e 10.35
Figu e 10. Ex ended LaMe mechanism, adap ed om Hube e al.
35 E. C. V eeland, J. Wa , G. B. Schobe , B. G. Hance, M. J. Aus in, A. D. P ice, B. D. Fellows,
T. C. Monson, N. S. Hudak, L. Maldonado-Cama go, A. C. Boho quez, C. Rinaldi, D. L.
Hube , Chem. Ma e . 2015, 27, 6059-6066.

Gene al In oduc ion
15
This p oposed mechanism, known as he Ex ended LaMe mechanism (Figu e
10), sugges s ha i he eac ion occu s in an open sys em wi h con inuous addi ion o
p ecu so , s ages I and II emain unchanged. Howe e , he concen a ion o monome
dec eases in a modi ied s age III un il i s abilises o e ime. This in oduces a new
s age IV, whe e nanopa icles g ow h occu s, allowing o a be e con ol o e size
dis ibu ion.
The LaMe mechanism and i s de i a i es a e no he only mechanisms p oposed
o explain nanopa icle o ma ion, as men ioned a he beginning o his sec ion. Finke
e al. desc ibed a wo-s ep mechanism in which a slow nuclea ion p ocess, ini ia ed
by species A ( he monome ), is ollowed by a as e au oca aly ic su ace g ow h o
species B ( he nanopa icle), as illus a ed in Scheme 1.36 Al hough his me hod does
no align wi h he classical nuclea ion concep s o he LaMe mechanism, bo h
p io i ise unde s anding nanopa icle g ow h h ough monome a achmen in
solu ion.
Scheme 1. Nanopa icles o ma ion acco ding o he wo-s ep mechanism p oposed
by Finke e al.
Conside ing he di e en p oposed mechanisms, nanopa icles o ma ion can
be simpli ied in o wo essen ial s eps: nuclea ion and g ow h. Bo h s eps can be
in luenced by ac o s such as empe a u e, ime and p ecu so employed. In his
con ex , he use o p epa a ion me hodologies ha enables he ep oducible o ma ion
o nanopa icles in e ms o size, shape, and su ace s a e is c ucial.37 Some examples
o exis ing me hodologies o nanopa icle p epa a ion will be discussed in he nex
sec ion.
36 M. A. Wa zky, R. G. Finke, Chem. Ma e . 1997, 9, 3083-3095.
37 M. Sajid, J. Plo ka-Wasylka, Mic ochem. J. 2020, 154, 104623.
Chap e I
16
1.3.2 Top-down and bo om-up me hodologies
Me al nanopa icles can be syn hesised h ough a ious ou es, which can be
classi ied in o wo main g oups: op-down and bo om-up me hodologies (Figu e 11).
In op-down me hodologies (Figu e 11a), a bulk ma e ial, ypically a solid,
is minia u ised using physical echniques un il i eaches he nanoscale. These op-
down echniques a e conside ed des uc i e app oaches o nano ab ica ion. While
hey a e well-sui ed o la ge-scale p oduc ion o nanopa icles, hey may no be ideal
o p oducing e y uni o m, egula and small pa icles. Some examples o echniques
employing a op-down app oach include nanoli hog aphy, spu e ing deposi ion and
lase abla ion.38
Figu e 11. Schema ic ep esen a ion o op-down (a) and bo om-up (b)
me hodologies o nanopa icle syn hesis.
Nanoli hog aphy: This g oup o echniques enables he modi ica ion o a
subs a e a he nanoscale using pa e ns de i ed om a empla e.39,40 Nanoli hog aphy
is commonly used o p epa e s uc u es a ound 20 nm, while sizes below 10 nm can
38 N. Abid, A. M. Khan, S. Shujai , K. Chaudha y, M. Ik am, M. Im an, J. Haide , M. Khan,
Q. Khan, M. Maqbool, Ad . Colloid In e ace Sci. 2022, 300, 102597.
39 D. Wou e s, U. S. Schube , Angew. Chem. In . Ed. 2004, 43, 2480-2495.
40 D. Resnick in Nanoli hog aphy: The A o Fab ica ing Nanoelec onic and Nanopho onic
De ices and Sys ems, Chap e 9, 315-347, M. Feldman (Ed), Woodhead Publishing, 2014.
Gene al In oduc ion
17
be achie ed employing speci ic echniques such as Ex eme Ul a iole In e e ence
Li hog aphy (EUV-IL).41
Spu e ing deposi ion: In his p ocess, a a ge su ace is bomba ded wi h ions
in he gas phase, esul ing in he physical expulsion o small pa icles.42 This echnique
has been used o p epa e s able colloidal me al nanopa icles in ionic liquids, showing
a clea size dependence based on he ionic liquid employed.43
Lase Abla ion: In his echnique, a lase se es as ene gy sou ce o emo e
su ace a oms om a solid. When he lase is ocused on a speci ic spo , he
empe a u e apidly inc eases, leading o localised apo isa ion o he s a ing
ma e ial. Subsequen collisions be ween he apo ised species ( ee a oms, molecules,
o ions) c ea e a plasma plume a e y high empe a u e (> 5000 K) which is hen
quenched o oom empe a u e. Nuclea ion o he sa u a ed apo ul ima ely esul s in
he o ma ion o nanosized pa icles.44
On he o he hand, bo om–up echniques (Figu e 11b) use e y small
pa icles ( ee a oms o molecules) as building blocks o o m nanopa icles.37 This
cons uc ion occu s in a con olled manne , enabling he p oduc ion o nanopa icles
ha a e homogeneous in size, shape and su ace s a e. Some examples o bo om-up
syn hesis p ocedu es include chemical apou deposi ion (CVD), me al sal educ ion,
sol-gel syn hesis and he o ganome allic app oach. The la e me hod is he one
selec ed o he p epa a ion o me al nanopa icles in his PhD hesis.
Chemical Vapou Deposi ion/Chemical Vapou Syn hesis: In CVD
echniques, hin ilms a e p epa ed on a subs a e ia chemical eac ions in ol ing
p ecu so s eleased in he gas phase.45 Howe e , nanopa icles can also be p oduced
41 W. Ka im, S. A. Tschupp, M. Oezaslan, T. J. Schmid , J. Gob ech , J. A. an Bokho en, Y.
Ekinci, Nanoscale 2015, 7, 7386-7393.
42 H. Wende , P. Migowski, A. F. Feil, S. R. Teixei a, J. Dupon , Coo d. Chem. Re . 2013, 257,
2468-2483.
43 T. To imo o, K. Okazaki, T. Kiyama, K. Hi aha a, N. Tanaka, S. Kuwaba a, Appl. Phys.
Le e s 2006, 89, 243117.
44 E. Mzwd, N. M. Ahmed, N. Su adi, S. K. Alsaee, A. S. Al owyan, M. A. Almessie e, A. F.
Oma , Scien i ic Repo s 2022, 12, 10549-10559.
45 L. Sun, G. Yuan, L. Gao, J. Yang, M. Chhowalla, M. H. Gha ahcheshmeh, K. K. Gleason,
Y. S. Choi, B. H. Hong, Z. Liu, Na . Re . Me hods P ime s 2021, 1, 5-24.
18
Chap e I
by adjus ing speci ic eac ion condi ions such as e y high empe a u es, high pa ial
p essu es o monome s, he use o small molecules as subs a es and long esidence
imes o he apou in he eac o . These longe esidence imes can be achie ed by
employing low gas lows o using long eac o s. Unde hese condi ions, he echnique
is known as Chemical Vapou Syn hesis (CVS). The mean sizes o he pa icles
p epa ed h ough CVS a e s ongly dependen on he na u e o he nanopa icles, and
o en exhibi signi ican size dispe si y. Fo example, CVS has been employed o
p epa e ZnO nanopa icles anging om 6 o 30 nm, as well as WS2 NPs wi h mean
sizes be ween 20 and 70 nm.46
Me al Sal Reduc ion: In his me hodology, a me al sal is educed employing
a educing agen (such as H2, CO, o NaBH4) in he p esence o an app op ia e
s abilising agen . This s abilise con ols he nuclea ion p ocess o he me al a oms and
acili a es he o ma ion o nanopa icles wi h a na ow size dis ibu ion and in high
yield.47,48
Sol-Gel: In a ypical sol-gel syn hesis, a molecula p ecu so is suspended in
wa e o alcohol, o ming a sol ich in colloidal s uc u es. This sol unde goes a
hyd olysis/alcoholysis o o m a nanopo ous s uc u e (gel), which is subsequen ly
calcined o achie e he inal nanoma e ial.49
1.3.3 O ganome allic app oach in nanopa icle syn hesis
The o ganome allic app oach, p ima ily de eloped by Chaud e and
collabo a o s,50 is a syn he ic p ocedu e based on he decomposi ion o an
o ganome allic p ecu so unde mild p essu e and empe a u e condi ions, and in he
46 C. Dhand, N. Dwi edi, X. J. Loh, A. N. J. Ying, N. K. Ve ma, R. W. Beue man, R.
Lakshmina ayanan, S. Ramak ishna, RSC Ad . 2015, 5, 105003-105037.
47 A. Roucoux, J. Schulz, H. Pa in, Chem. Re . 2002, 102, 3757-3778.
48 Y. Yu, W. Yang, X. Sun, W. Zhu, X. Z. Li, D. J. Sellmye , S. Sun, Nano Le . 2014, 14, 2778-
2782.
49 F. Hu, Z. Hu, Y. Liu, K. C. Tam, R. Liang, Q. Xie, Z. Fan, C. Pan, J. Tang, G. Yu, W. Zhang,
J. Am. Chem. Soc. 2023, 145, 27718-27727.
50 K. Philippo , B. Chaud e , in Comp ehensi e O ganome allic Chemis y III, R. H. C ab ee
& M. P. Mingos (Eds-in-Chie ); Applica ions III: Func ional Ma e ials, En i onmen al and
Biological Applica ions, D. O´Ha e (Volume Ed.), Vol 12, Chap e 03, 71-99, Else ie , 2007.
19
Gene al In oduc ion
p esence o a s abilising agen . This s abilise can be a polyme , an o ganic ligand,
solid suppo s, o he sol en o he eac ion in speci ic cases. The main ad an age o
his me hodology is he p oduc ion o me al nanopa icles (MNPs) wi h well-
con olled sizes and shapes, and clean su aces. Scheme 2 summa ises his p ocess,
dis inguishing h ee s eps: a) decomposi ion o he o ganome allic p ecu so by H2 o
ano he educing agen , eleasing naked me allic a oms in o he eac ion medium, b)
nuclea ion o hese naked a oms, and c) g ow h o he nanopa icles, which is
con olled by he s abilise agen .
Scheme 2. O ganome allic app oach o he syn hesis o me al nanopa icles.
The use o o ganome allic complexes con aining ze o o low- alen me al as
p ecu so s acili a es hei decomposi ion unde milde condi ions compa ed o me al
sal s. Va ious ypes o complexes can be employed, wi h ole inic ones being he mos
common. Unde hyd ogen p essu e, he unsa u a ed ligands in he coo dina ion sphe e
o he me al a e educed o alkanes, allowing o he easy elease o naked a oms in o
he medium, e en a oom empe a u e.51 These a oms o m clus e s du ing he
nuclea ion p ocess and subsequen ly g ow o o m MNPs. S abilising ligands play a
key ole in he o ma ion o he pa icles, p e en ing me al coalescence and enabling
he o ma ion o well-con olled nanopa icles in e ms o size, shape, and su ace
51 C. Amiens, B. Chaud e , D. Ciuculescu-P adines, V. Colliè e, K. Faje we g, P. Fau, M. Kahn,
A. Maisonna , K. Soulan ica, K. Philippo , New J. Chem. 2013, 37, 3374-3401.

20
Chap e I
s a e.52 Addi ionally, he use o H2 as a educing agen esul s in he p esence o
hyd ides on he su ace o hese o ganome allic nanopa icles, which signi ican ly
in luences hei eac i i y.
Di e en o ganome allic p ecu so s ha e been employed in he li e a u e o
he p epa a ion o MNPs. Some examples o o ganome allic p ecu so s ha ha e been
success ully used as s a ing ma e ials include [P (dba)2] (dba =
dibenzylideneace one) and [Ru(COD)(COT)] (COD = 1,5-cyclooc adiene; COT =
1,3,5-cyclooc a iene), bo h o which yield sphe ical and small nanopa icles (1-2
nm).53,54 Complexes con aining a yl o alkyl subs i uen s, such as [P (CH3)2(COD)],
a e mo e challenging o decompose due o hei highe s abili y. Howe e , his
p ope y can be employed o p epa e la ge nanopa icles (25-75 nm) wi h shapes like
cubes o a ows, exposing (100) o (111) aces.55
Ca bonyl complexes a e also sui able as o ganome allic p ecu so s o he
syn hesis o me al NPs. Howe e , since CO ac s as bo h a σ-dono and a π-accep o
ligand, i s coo dina ion ene gy inc eases, making comple e elimina ion om he me al
coo dina ion sphe e challenging. The e o e, he syn hesis o nanopa icles in ol ing
CO complexes as p ecu so s, such as [Fe(CO)5], may equi e ha she condi ions,
including high empe a u es o he use o ul asounds, and con olling hei size can
be complica ed. Despi e hese challenges, [Fe(CO)5] has been success ully u ilised in
he p epa a ion o nanopa icles wi h magne ic hype he mia p ope ies.56
Al hough no s ic ly o ganome allic species, coo dina ion complexes
con aining amide ligands can also be employed as p ecu so s, as hey can be
52 B. Co ma y, F. Dumes e, N. Liakakos, K. Soulan ica, B. Chaud e , Dal on T ans. 2013, 42,
12546-12553.
53 C. Pan, K. Pelze , K. Philippo , B. Chaud e , F. Dassenoy, P. Lecan e, M. J. Casano e, J.
Am. Chem. Soc. 2001, 123, 7584-7593.
54 A. Rod íguez, C. Amiens, B. Chaud e , M. J. Casano e, P. Lecan e, J. S. B adley, Chem.
Ma e . 1996, 8, 1978-1986.
55 M. R. Axe , K. Philippo , B. Chaud e , M. Cabié, S. Gio gio, C. R. Hen y, Small 2011, 7,
235-241.
56 A. Me e, B. Mehdaoui, V. Kelsen, P. F. Fazzini, J. Ca ey, S. Lachaize, M. Respaud, B.
Chaud e , Nano Le . 2012, 12, 4722-4728.
Gene al In oduc ion
21
decomposed unde H2 p essu e. Some o he mos cha ac e is ic complexes in his
ca ego y include Fe[N(SiMe3)2]2 and Co[N(SiMe3)2]2.52
Ni,57 Ru,58 P ,59 Pd,60 Co,61 o I 62 NPs ha e been success ully ob ained
applying he o ganome allic me hodology. While he choice o he p ecu so is
essen ial o de e mining he na u e o he nanopa icles, he s abilising agen
employed is c ucial, as i was men ioned p e iously.63 These agen s can a y
signi ican ly in hei na u e, composi ion and s abilisa ion modes.
1.4 S abilisa ion o nanopa icles
Nanopa icles, like o he nanoma e ials, exhibi high su ace o olume and
su ace o mass a ios compa ed o hei bulk ma e ials. As men ioned, he p ope ies
o NPs a e la gely dependen on hei size, pa icula ly in ca aly ic applica ions. Fo
such pu poses, i is desi able o ob ain NPs as small as possible; howe e , smalle
pa icles end o ha e low he modynamic s abili y and can easily agglome a e, due o
Van de Waals o ces.64 This beha iou leads o he o ma ion o la ge , mo e s able
pa icles, which consequen ly lose some o hei unique p ope ies. To coun e his,
he addi ion o an agen capable o inhibi ing he o ma ion o excessi ely la ge
pa icles o me al agglome a es is essen ial o syn hesising nanopa icles.
S abilisa ion modes o nanopa icles a e commonly classi ied in o i e ca ego ies: (a)
elec os a ic, (b) s e ic, (c) elec os e ic, (d) s abilisa ion by solid suppo s, and (e)
s abilisa ion by ligands (Figu e 12).47,65
57 D. Bouzoui a, J. M. Asensio, V. P ei e , A. Palazzolo, P. Lecan e, G. Pie e s, S. Feuillas e,
S. T ica d, B. Chaud e , Nanoscale 2020, 12, 15736-15742.
58 P. Molinillo, B. Lac oix, F. Va ie , N. Rendón, A. Suá ez, P. La a, Chem. Commun. 2022,
58, 7176-7179.
59 P. La a, K. Philippo , A. Suá ez, ChemCa Chem 2019, 11, 766-771.
60 N. J. S. Cos a, M. Gue e o, V. Colliè e, E. Teixei a-Ne o, R. Lande s, K. Philippo , L. M.
Rossi, ACS Ca al. 2014, 4, 1735-1742.
61 L. M. Ma ínez-P ie o, J. Ma baix, J. M. Asensio, C. Ce ezo-Na a e e, P. Fazzini, K.
Soulan ica, B. Chaud e , A. Co ma, ACS Appl. Nano Ma e . 2020, 3, 7076-7087.
62 A. Zuluaga-Villamil, G. Mencia, J. M. Asensio, P. Fazzini, E. A. Baque o, B. Chaud e ,
O ganome allics 2022, 41, 3313-3319.
63 P. La a, K. Philippo , B. Chaud e , ChemCa Chem 2013, 5, 28-45.
64 L. S. O , R. G. Finke, Coo d. Chem. Re . 2007, 251, 1075-1100.
65 S. Na h, S. Jana, M. P adhan, T. Pal, J. Colloid In e ace Sci. 2010, 341, 333-352.
Chap e I
22
Figu e 12. S abilisa ion modes o nanopa icles.
1.4.1 Elec os a ic s abilisa ion
Elec os a ic s abilisa ion a ises om cha ged pa icles, such as halides,
ca boxyla es, o simila ions and ypically akes place in an aqueous solu ion. These
anions adso b on he nanopa icle su ace, c ea ing a double laye ha gene a es
coulombic epulsion be ween pa icles. When his coulombic epulsion balances Van
de Waals o ces, he o ma ion o me al agglome a es is p e en ed, esul ing in a
s able colloid.66 An example o his s abilisa ion mode is he case o Ag2S
nanopa icles s abilised by sulphu ions desc ibed by Kuzne so a e al.67
1.4.2 S e ic s abilisa ion
S e ic s abilisa ion occu s when me al a oms a e su ounded by
mac omolecules such as polyme s o dend ime s. The s uc u e o hese
mac omolecules, which con ain ca i ies, acili a es he nuclea ion p ocess and he
66 S. Anboo, S. Y. Lau, J. Kansedo, P.-S. Yap, T. Hadiba a a, A. H. Kama uddin, Heliyon 2024,
10, e27348.
67 Y. V. Kuzne so a, I. A. Balyakin, I. D. Popo , B. Schumme , B. Socho , S. V. Rempel, A. A.
Rempel, J. Mol. Liq. 2021, 335, 116130.
Gene al In oduc ion
23
g ow h o he nanopa icles wi hin hem. In he in e pa icle space, he mo emen o
he nanopa icles, in luenced by Van de Waals o ces, is s e ically es ic ed he eby
p e en ing agglome a ion. Non-pola sol en s a e gene ally mo e sui able o his ype
o s abilisa ion.47 Va ious me al nanopa icles, including hose based on Ni, Ru and
P , s abilised by he polyme poly inylpy olidone (PVP), ha e been epo ed in he
li e a u e.63,68,69
1.4.3 Elec os e ic s abilisa ion
Elec os e ic s abilisa ion akes place when elec os a ic and s e ic
s abilisa ion modes a e combined. This can be achie ed, o example, by using ionic
polyme s ha con ain pola g oups along wi h side chains capable o gene a ing bo h
s e ic and coulombic epulsion simul aneously. A no able example is he s abilising
ole o sodium polyac yla e in he p epa a ion o ba i e nanopa icles.47,70
1.4.4 S abilisa ion by solid suppo s
In his s abilisa ion mode, nanopa icles a e con ined wi hin a solid, which
es ic s hei mo emen and p e en s agglome a ion. Va ious syn he ic p ocedu es
can be used o p epa e suppo ed me al nanopa icles, such as imp egna ion, g a ing,
lame sp aying, o ion exchange.71 Fo ins ance, suppo ed u henium nanopa icles
on di e en ca bon nano ubes ha e been desc ibed by P. Se p e al.72
1.4.5 S abilisa ion by ligands.
Co alen in e ac ions be ween he su ace o he pa icles and he ligands
p e en a ac i e o ces be ween he pa icles and p o ec hem om coalescence.63,65
68 D. Özha a, N. Z. Kiliçaslan, S. Özka , Appl. Ca al. B: En i on. 2015,162, 573-582.
69 F. Dassenoy, K. Philippo , T. O. Ely, C. Amiens, P. Lecan e, E. Snoeck, A. Mosse , M.
Casano e, B. Chaud e , New J. Chem. 1998, 22, 703-711.
70 J. Hang, L. Shi, X. Feng, L. Xiao, Powde Technology 2009, 192, 166-170.
71 C. Jia, F. Schü h, Phys. Chem. Chem. Phys. 2011, 13, 2457-2487.
72 D. M. Fe nandes, M. Rocha, C. Ri e a-Cá camo, P. Se p, C. F ei e, Dal on T ans. 2020, 49,
10250-10260.
30
Chap e I
Å) and sa u a ed C2-N (1.49 Å).95,99 Finally, pa ial a oma ici y adds addi ional
elec onic s abilisa ion.
Figu e 17. Elec onic s uc u e o imidazol-2-ylidenes.
Today, one o he mos compelling ad an ages o using ca benes as ligands in
o ganome allic chemis y elies on he ease wi h which s uc u ally di e se analogues
can be syn hesised. In addi ion o imidazol-2-ylidenes (A duengo ype ca benes),
exis s a wide a ie y o N-he e ocyclic ca benes including 1,2,3- iazolylidenes
( ep esen a i e examples o mesoionic ca benes, MIC), imidazolin-2-ylidenes, o 2-
py idylidenes, among o he s (see Figu e 18). Some o hese ca benes a e e e ed o
as abno mal o emo e when hei s uc u al ep esen a ion equi es he in oduc ion
o o mal cha ges o lacks a he e oa om adjacen o he ca benic a om. No ably, some
o hese species emain non-isolable, pa icula ly many mesoionic ca benes.100,101 I
has been gene ally obse ed ha MIC ligands a e s onge dono s han classical
NHCs. This enhanced dono s eng h has been quan i ied using di e en echniques,
p ima ily by spec oscopic me hods. Fo ins ance, ca bonyl complexes con aining a
ca bene coo dina ed o he me al ha e been s udied h ough IR spec oscopy. The
analysis o CO s e ching ib a ions in complexes con aining a mesoionic ligand
99 J. W. Runyon, O. S einho , H. V. R. Dias, J. C. Calab ese, W. J. Ma shall, A. J. A duengo,
Aus . J. Chem. 2011, 64, 1165-1172.
100 O. Schus e , L. Yang, H. G. Raubenheime , M. Alb ech , Chem. Re . 2009, 109, 3445-3478.
101 E. S ande -G oble , O. Schus e , G. Heyden ych, S. C onje, E. Tosh, M. Alb ech , G.
F enking, H. G. Raubenheime , O ganome allics 2010, 29, 5821-5833.

31
Gene al In oduc ion
e eals an a e age ib a ional CO equency ha is lowe han ha o complexes wi h
an A duengo- ype ca bene. This beha iou e eals s onge dono p ope ies in he
case o MICs.102 Simila indings ha e been epo ed using X- ay Pho oelec on
Spec oscopy (XPS), which e ealed ha he binding ene gies o palladium 3d
pho oemission a e gene ally lowe when he me al is coo dina ed o mesoionic
ca benes han o he complexes wi h imidazol-2-ylidenes, indica ing a highe elec on
densi y in he me al cen e due o s onge dono p ope ies o he iazolylidene
ligand.103 These s onge dono p ope ies make mesoionic ligands pa icula ly
a ac i e as s abilise s o nanopa icles.
Figu e 18. Rep esen a i e examples o NHC ligands.
Mos applica ions o ca benes in ol e hei coo dina ion o ansi ion me als,
whe he in molecula complexes o me al nanopa icles.104 Al hough he e a e
examples o he di ec use o NHCs as o ganoca alys s in eac ions in ol ing a
nucleophilic a ack on es e s, aldehydes o o he ca bon compounds,105 a discussion
o ha applica ion alls ou side he scope o his PhD hesis. Since his hesis ocuses
on nanopa icles syn hesised using he o ganome allic app oach, he discussion will
cen e on he epo ed syn he ic me hods in ol ing NHC-s abilised o ganome allic
nanopa icles.
102 A. Vi ancos, C. Sega a, M. Alb ech , Chem. Re . 2018, 118, 9493-9586.
103 T. Te ashima, S. Inoma a, K. Oga a, S. Fukuzawa, Eu . J. Ino g. Chem. 2012, 1387-1393.
104 S. Díez-González, N. Ma ion, S. P. Nolan, Chem. Re . 2009, 109, 3612-3676.
105 D. Ende s, O. Niemeie , A. Hensele , Chem. Re . 2007, 107, 5606-5655.
Chap e I
32
The e a e wo main syn he ic app oaches o s abilising me al nanopa icles
wi h NHC ligands. The i s implies he p io isola ion o he ee ca bene, which is
hen used as s abilise in he p esence o an o ganome allic p ecu so ha decomposes
unde hyd ogen gas. This app oach was i s epo ed by P. La a, K. Philippo , B.
Chaud e e al.106 The NHC-s abilised u henium nanopa icles desc ibed in ha wo k,
summa ised in Scheme 3, we e ob ained by decomposi ion o [Ru(COD)(COT)]
unde 3 ba o H2 in he p esence o 0.2 o 0.5 equi . o wo di e en imidazol-2-
ylidene ca benes: 1,3-bis(2,6-diisop opylphenyl)imidazol-2-ylidene (IP ) and 1,3-
di( e -bu yl)imidazol-2-ylidene (I Bu). This p ocess esul ed in he o ma ion o
nanopa icles wi h a mean size o ca 1.5 nm. La e , Goda d e al. epo ed a simila
p o ocol o he syn hesis o hodium nanopa icles om [Rh(C3H5)3] also s abilised
by IP , yielding nanopa icles wi h a mean size be ween 1.3 and 1.7 nm, which
demons a ed ca aly ic ac i i y in educ ion eac ions.107 Building on hese p eceden s,
he use o simila ligands has been ex ended o o he me als. Today, ca benes a e
among he mos commonly employed amilies o ligands o s abilising
nanopa icles.108
106 P. La a, O. Ri ada-Wheelaghan, S. Coneje o, R. Po eau, K. Philippo , B. Chaud e , Angew.
Chem. In . Ed. 2011, 123, 12286-12290.
107 F. Ma ínez-Espina , P. Blondeau, P. Nolis, B. Chaud e , C. Cla e , S. Cas illón, C. Goda d,
J. Ca al. 2017, 354, 113-127.
108 H. Shen, G. Tian, Z. Xu, L. Wang, Q. Wu, Y. Zhang, B. K. Teo, N. Zheng, Coo d. Chem.
Re . 2022, 458, 214425.
Gene al In oduc ion
33
Scheme 3. O ganome allic syn hesis o Ru·IP and Ru·I Bu NPs.
As p e iously men ioned, many NHC ligands a e no isolable due o hei high
eac i i y, which limi s he applicabili y o he p ocedu e ou lined in he p e ious
pa ag aph. To o e come his incon enience, a new app oach was p oposed by K.
Philippo , B. Chaud e e al.,109 ocused on he in-si u o ma ion o he ca bene. A e
dep o ona ing he co esponding imidazolium sal wi h a s ong base, he esul ing
NHC is il e ed h ough celi e and ans e ed o a Fishe -Po e eac o con aining he
p ecu so . A emp s o explo e his app oach wi h isolable ca benes e ealed e y
simila mean sizes o nanopa icles p epa ed by bo h me hods, leading o i s
accep ance as an app op ia e syn he ic p ocess o non-isolable ca benes.
In addi ion o using isola ed ca benes o gene a ing hem in-si u,
deca boxyla ion o a ca bene p ecu so , such as 1,3-dialkylimidazolium-2-
ca boxyla e, and i s use as s abilise o nickel nanopa icles has also been epo ed.110
Howe e , due o he limi ed a ailabili y o sui able p ecu so s o be deca boxyla ed,
his me hod cu en ly appea s o be mo e anecdo al.111
109 L. M. Ma ínez-P ie o, A. Fe y, P. La a, C. Rich e , K. Philippo , F. Glo ius, B. Chaud e ,
Chem. Eu . J. 2015, 21, 17495-17502.
110 M. Díaz de los Be na dos, S. Pé ez-Rod íguez, A. Gual, C. Cla e , C. Goda d, Chem.
Commun. 2017, 53, 7894-7897.
111 C. Ce ezo-Na a e e, P. La a, L. M. Ma ínez-P ie o, Ca alys s 2020, 10, 1144.
Chap e I
34
1.5 Cha ac e isa ion o me al nanopa icles
This sec ion p o ides a b ie o e iew o he main cha ac e isa ion echniques
employed in his PhD hesis.
1.5.1 T ansmission Elec on Mic oscopy (TEM and HRTEM)
T ansmission Elec on Mic oscopy (TEM) is a key analy ical echnique used
o de e mine he size, shape, and dispe si y o nanopa icles. This echnique in ol es
deposi ing a d op o a colloidal nanopa icle suspension on o a coppe g id, which is
hen in oduced in o he mic oscope. Unlike adi ional op ical mic oscopy, which
elies on pho ons o illumina e he sample, TEM mic oscope uses an elec on beam o
i adia e he sample. A po ion o he elec ons is ansmi ed h ough he sample,
while he es a e sca e ed. The esul ing image is gene a ed om he in o ma ion
acqui ed by he ansmi ed elec ons. High Resolu ion T ansmission Elec on
Mic oscopy (HRTEM) ope a es on he same p inciples bu allows he de e mina ion
o he c ys alline s uc u e o he pa icles by pe o ming he analysis a a highe
magni ica ion.112,113
1.5.2 Scanning T ansmission Elec on Mic oscopy (STEM)
Scanning T ansmission Elec on Mic oscopy (STEM) is a echnique simila
o con en ional TEM, bu i ocuses he elec on beam on a na ow spo ha is scanned
ac oss he sample. The image is o med by collec ing he ansmi ed elec ons. STEM
is pa icula ly sui ed o High-Angle Annula Da k-Field scanning (HAADF), which
cap u es sca e ed elec ons a high angles. HAADF images a e highly sensi i e o
a omic numbe , allowing hea ie elemen s o be obse ed wi h g ea e con as
compa ed o ligh e elemen s. When combined wi h an Ene gy-Dispe si e X- ay
spec oscopy (EDX) de ec o , STEM enables he ob en ion o elemen al maps,
p o iding aluable in o ma ion abou he chemical composi ion o he sample.112
112 S. Mou dikoudis, R. M. Palla es, N. T. K. Thanh, Nanoscale 2018, 10, 12871-12934.
113 D. Su, G een Ene gy En i on. 2017, 2, 70-83.
Gene al In oduc ion
35
1.5.3 Induc i ely Coupled Plasma (ICP)
Induc i ely Coupled Plasma is a selec i e echnique widely used o he
elemen al analysis o nanopa icles, hanks o i s ul alow de ec ion limi , ypically in
he o de o ng·L-1, and minimal sample consump ion. Sample p epa a ion gene ally
in ol es decomposing he nanopa icles and o ganic ma ix h ough diges ion wi h
ni ic, hyd ochlo ic, sulphu ic acid, o simila des uc i e ea men s. Once a lique ied
sample is ob ained, a ca ie gas deli e s i in o an a gon plasma o ch, whe e
ionisa ion o he chemical elemen s occu s. A Mass Spec ome e hen sepa a es he
ions based on hei mass- o-cha ge a io, enabling he iden i ica ion o he di e en
componen s.114,115
1.5.4 X- ay Pho oelec on Spec oscopy (XPS)
X- ay Pho oelec on Spec oscopy (XPS) is an analy ical echnique employed
o su ace chemical analysis. The echnique is based on he pho oelec ic e ec : when
a sample is i adia ed wi h X- ay, pho oelec ons a e emi ed om i s su ace. The
XPS spec um is ob ained by measu ing he numbe and kine ic ene gy o hese
pho oelec ons, which can be co ela ed o hei binding ene gies. By analysing hese
binding ene gies, di e en species p esen on he sample su ace can be iden i ied and
quan i ied. The species composing he sample su ace can be iden i ied and quan i ied
by conside ing a ia ions in hei oxida ion s a e and/o chemical na u e. This
echnique equi es ul a-high acuum condi ions (a ound 10-9 mba ) and eaches a
dep h o app oxima ely 2-5 nm.116
1.6. Ca alysis by me al nanopa icles
As p e iously men ioned, he in e es o me al nanopa icles is d i en by hei
po en ial applica ions ac oss di e en ields such as op oelec onics, sensing,
114 N. V. Godoy, R. M. Galazzi, K. Chacón-Mad id, M. A. Z. A uda, I. O. Mazali, Talan a
2021, 224, 121808.
115 B. Mee mann, V. Nischwi z, J. Anal. A . Spec om. 2018, 33, 1432-1468.
116 J. Zheng, Y. Lyu, B. Wu, S. Wang, Ene gyChem 2020, 2, 100039.

Chap e I
36
biomedicine, ca alysis, and ene gy con e sion o s o age.117,118 The use o me al
nanopa icles as ca alys s in chemical eac ions is expanding an a ea o esea ch in
con empo a y chemis y.
The adi ional dis inc ion be ween he e ogeneous and homogeneous ca alysis
is based on he physical s a e o he eac an s. In homogeneous ca alysis, he ca alys
and subs a e a e in he same physical s a e, whe eas in he e ogeneous ca alysis, he
ca alys is in a di e en physical s a e om he eac an s.
In he case o nanos uc u ed ca alys s, applying his classical dis inc ion
be ween homogeneous and he e ogenous na u e can be complex.119 Nanopa icles
exhibi some homogeneous p ope ies, such as mobili y in solu ion, as well as
he e ogeneous p ope ies, such as he p esence o a liquid-solid in e ace. Since he
la e 20 h cen u y, esea che s like Schwa z, Ree z and o he s ha e employed a
de ini ion based on he numbe o di e en ac i e si es a ailable on a gi en
ca alys .120,121,122 When a ca alys possesses only one ype o ac i e si e, is conside ed
homogeneous; con e sely, when mul iple ypes o ac i e si es a e p esen , i is
classi ied as he e ogeneous. Gi en ha nanopa icles inhe en ly possess mul iple
ac i e si es, such as co ne s, edges, o di e en exposed c ys al aces, hey a e
classi ied as he e ogeneous ca alys s acco ding o his de ini ion.123 Howe e , i is also
known ha some nanopa icles in solu ion can gene a e di e en me allic complexes
ha a e he ac ual ca aly ic species due o hei dynamic beha iou . In his sense,
nanopa icles can exhibi cha ac e is ics like homogeneous ca alys s. The e o e, i is
o en p e e able o e e o nanopa icles as colloidal ca alys s, dis inguishing hei
beha iou om ha o he e ogeneous and homogeneous ca alys s.
117 A. S. Galushko, A. S. Kashin, D. B. E emin, M. V. Polynski, E. O. Pen sak, V. M.
Che nyshe , V. P. Ananiko in Nanopa icles in Ca alysis: Ad ances in Syn hesis and
Applica ions, Chap e 2, 13-42, K. Philippo , A. Roucoux (Eds), Wiley-VCH, 2021.
118 M. R. Axe , K. Philippo , Chem. Re . 2020, 120, 1085-1145.
119 C. Tabo , R. Na ayanan, M. A. El-Sayed, in Model Sys ems in Ca alysis: Single C ys als o
Suppo ed Enzyme Mimics, Chap e 18, 395-414, R. Rioux (Ed), Sp inge , 2010.
120 J. Schwa z, Acc. Chem. Res. 1985, 18, 302-308.
121 M. T. Ree z, R. B einbau , P. Wedemann, P. Binge , Te ahed on 1998, 54, 1233-1240.
122 J. D. Aiken, Y. Lin, R. G. Finke, J. Mol. Ca al. A Chem. 1996, 114, 29-51.
123 J. A. Wideg en, R. G. Finke, J. Mol. Ca al. A Chem. 2003, 198, 317-341.
37
Gene al In oduc ion
Me al nanopa icles a e a ac i e species in ca alysis due o hei high su ace
o olume a io, which is especially p onounced in smalle nanopa icles, o e ing a
as numbe o po en ial ac i e si es. Gene ally, a smalle pa icle size and lowe
su ace co e age a e co ela ed wi h enhanced ca aly ic ac i i y, making c ucial he
op imisa ion o he balance be ween hese ac o s o e ec i e ca alys design. Fo a
gi en ligand, he mean size o he esul ing nanopa icles dec eases wi h inc easing
ligand quan i y. Howe e , his also leads o g ea e su ace co e age by he ligand,
which can nega i ely impac ca aly ic ac i i y.111 The o ien a ion o he c ys alline
planes exposed a he nanopa icle su ace, in luenced by he nanopa icle shape,
signi ican ly a ec s ca aly ic p ope ies.118,124,125 Fo example, i has been epo ed ha
in hyd ogena ion eac ions employing benzene as subs a e, he selec i i y o he
p ocess depends on he exposed planes. In such case, pla inum nanoc ys als ha
expose bo h (100) and (111) c ys alline planes can p oduce cyclohexane and
cyclohexene, while nanoc ys als ha show only (100) plane selec i ely p oduced
cyclohexane.126
In addi ion o he p e iously men ioned pa ame e s, he composi ion o he
nanopa icle is ano he c i ical ac o ha in luences i s ca aly ic pe o mance, wi h
wo key con ibu ions: he na u e o he me allic co e and he s abilise used. The
composi ion mus be ailo ed based on he speci ic ca alysis a ge , as he choice o
he me allic co e can signi ican ly a ec eac i i y (ce ain me als a e well known o
speci ic ca aly ic applica ions while o he a e no ). A his espec , noble me als a e
pa icula ly enowned o hei ca aly ic p ope ies. Fo ins ance, gold nanopa icles
a e highly epu ed o CO oxida ion and alkene hyd ogena ion,127 while palladium
nanopa icles a e ex ensi ely employed in a wide ange o C—C coupling eac ions.128
124 A. K. Ben ley, S. E. Sk abalak, J. Chem. Educ. 2023, 100, 3425-3433.
125 H. G. Yang, C. H. Sun, S. Z. Qiao, J. Zou, G. Liu, S. C. Smi h, H. M. Cheng, G. Q. Lu,
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126 K. M. B a lie, H. Lee, K. Kom opoulos, P. Yang, G. Somo jai, Nano Le . 2007, 7, 3097-
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127 G. C. Bond in Gold Nanopa icles o Physics, Chemis y and Biology, Chap e 7, 171-197,
C. Louis and O. Pluche y (Eds), Impe ial College P ess, 2012.
128 I. Saldan, Y. Semenyuk, I. Ma chuk, O. Reshe nyak, J. Ma e . Sci. 2015, 50, 2337-2354.
Chap e I
38
Rhodium NPs a e aluable o hei applica ions in hyd ogena ion and
hyd o o myla ion eac ions,129 and i idium nanoca alys s a e highly e ec i e in wa e -
spli ing p ocesses.130 Howe e , in ecen yea s, he e has been an inc easing in e es
o non-noble me als (Fe, Co, Ni, Mn). F om a g een chemis y pe spec i e, hese
me als a e o en p e e ed due o hei lowe oxici y and g ea e abundance in he
Ea h’s c us , compa ed o hei expensi e and sca ce p ecious me al coun e pa s.131
The ca aly ic p ope ies o me als like i on, cobal , o nickel ha e been exploi ed o
a ious eac ions, including hyd ogena ion o N-he e oa enes, hyd olysis o
ammonia-bo ane, and oxygen educ ion eac ions in uel cells, among o he s.132,133,134
In addi ion o he na u e o he me al, he s abili y and e ec i eness o me al
nanopa icles a e signi ican ly in luenced by he choice o he s abilise employed, as
discussed in sec ion 1.4.5.118 Ligand in e ac ion wi h me al su ace (by s e ic o
elec onic e ec s) modula es i s p ope ies, playing a non-innocen ole.135 This
c ea es a pa allelism be ween colloidal ca alysis and homogeneous ca alysis. In his
con ex , selec ing he app op ia e me al, ligand and me al/ligand a io p esen s a
signi ican challenge.
Since he ini ial epo s o hei use, he e sa ili y o he o ganome allic
app oach, combined wi h a ho ough s udy o he ac o s in luencing ca aly ic
pe o mance, has led o he de elopmen o a wide a ie y o o ganome allic
nanoca alys s.50 Resea ch in o pla inum59 and u henium nanopa icles,106 as well as
nanopa icles s abilised by NHC ligands, has been pa icula ly uc i e ous.
129 M. Gue e o, N. T. T. Chau, S. Noël, A. Denicou -Nowicki, F. Hapio , A. Roucoux, E.
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131 V. Papa, Y. Cao, A. Spannenbe g, K. Junge, M. Belle , Na u e Ca alysis 2020, 3, 135-142.
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Gene al In oduc ion
39
Addi ionally, he e ha e been signi ican con ibu ions in ol ing 1s ow ansi ion
me al nanopa icles and magne ically induced nanoca alys s.61,136,137
Some ep esen a i e examples o ca aly ic eac ions ca ied ou wi h
o ganome allic nanopa icles include hyd ogena ion p ocesses, wa e spli ing
eac ions, magne ically induced ca alysis, hyd obo a ion o alkynes, H2 p oduc ion
om amine-bo anes, iso opic H/D exchange, Suzuki-Miyau a o o he Ca bon-
Ca bon Coupling eac ions and Fische -T opsch syn hesis (FTS), among o he s.138
Hyd ogena ion eac ions a e among he mos ex ensi ely s udied ca aly ic
p ocesses in ol ing o ganome allic nanopa icles. Nume ous ca alys s ha e been
de eloped ha exhibi op imal ac i i ies and selec i i ies. Fo ins ance, NHC-
s abilised pla inum nanopa icles ha e been used o selec i e hyd ogena ion o
ni oa enes wi hou a ec ing o he subs i uen s on he a oma ic ing.139 Simila ly,
bime allic cobal - hodium nanopa icles s abilised in Suppo ed Ionic Liquid Phases
(SILP) show ac i i y on hyd ogena ion o mul i unc ional subs a es.140 Bo h
examples a e illus a ed in Scheme 4 and Scheme 5, espec i ely.
Scheme 4. Selec i e hyd ogena ion o ni oa enes ca alysed by P -NHC NPs.
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110 M. Díaz de los Be na dos, S. Pé ez-Rod íguez, A. Gual, C. Cla e , C. Goda d,
Chem. Commun. 2017, 53, 7894-7897.
111 C. Ce ezo-Na a e e, P. La a, L. M. Ma ínez-P ie o, Ca alys s 2020, 10, 1144.
112 S. Mou dikoudis, R. M. Palla es, N. T. K. Thanh, Nanoscale 2018, 10, 12871-
12934.
113 D. Su, G een Ene gy En i on. 2017, 2, 70-83.
114 N. V. Godoy, R. M. Galazzi, K. Chacón-Mad id, M. A. Z. A uda, I. O. Mazali,
Talan a 2021, 224, 121808.
115 B. Mee mann, V. Nischwi z, J. Anal. A . Spec om. 2018, 33, 1432-1468.
116 J. Zheng, Y. Lyu, B. Wu, S. Wang, Ene gyChem 2020, 2, 100039.
Chap e I
50
117 A. S. Galushko, A. S. Kashin, D. B. E emin, M. V. Polynski, E. O. Pen sak, V. M.
Che nyshe , V. P. Ananiko in Nanopa icles in Ca alysis: Ad ances in Syn hesis and
Applica ions, Chap e 2, 13-42, K. Philippo , A. Roucoux (Eds), Wiley-VCH, 2021.
118 M. R. Axe , K. Philippo , Chem. Re . 2020, 120, 1085-1145.
119 C. Tabo , R. Na ayanan, M. A. El-Sayed, in Model Sys ems in Ca alysis: Single
C ys als o Suppo ed Enzyme Mimics, Chap e 18, 395-414, R. Rioux (Ed), Sp inge ,
2010.
120 J. Schwa z, Acc. Chem. Res. 1985, 18, 302-308.
121 M. T. Ree z, R. B einbau , P. Wedemann, P. Binge , Te ahed on 1998, 54, 1233-
1240.
122 J. D. Aiken, Y. Lin, R. G. Finke, J. Mol. Ca al. A Chem. 1996, 114, 29-51.
123 J. A. Wideg en, R. G. Finke, J. Mol. Ca al. A Chem. 2003, 198, 317-341.
124 A. K. Ben ley, S. E. Sk abalak, J. Chem. Educ. 2023, 100, 3425-3433.
125 H. G. Yang, C. H. Sun, S. Z. Qiao, J. Zou, G. Liu, S. C. Smi h, H. M. Cheng, G. Q.
Lu, Na u e 2008, 453, 638-642.
126 K. M. B a lie, H. Lee, K. Kom opoulos, P. Yang, G. Somo jai, Nano Le . 2007, 7,
3097-3101.
127 G. C. Bond in Gold Nanopa icles o Physics, Chemis y and Biology, Chap e 7,
171-197, C. Louis and O. Pluche y (Eds), Impe ial College P ess, 2012.
128 I. Saldan, Y. Semenyuk, I. Ma chuk, O. Reshe nyak, J. Ma e . Sci. 2015, 50, 2337-
2354.
129 M. Gue e o, N. T. T. Chau, S. Noël, A. Denicou -Nowicki, F. Hapio , A. Roucoux,
E. Mon lie , K. Philippo , Cu . O g. Chem. 2013, 17, 364-399.
130 a) J. Quinson, Ad . Colloid In e ace Sci. 2022, 303, 102643; b) G. Ma í, L.
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131 V. Papa, Y. Cao, A. Spannenbe g, K. Junge, M. Belle , Na u e Ca alysis 2020, 3,
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132 B. Sahoo, C. K eyenschul e, G. Agos ini, H. Lund, S. Bachmann, M. Scalone, K.
Junge, Chem. Sci. 2018, 9, 8134-8141.
Gene al In oduc ion
51
133 K. Kuma , P. Gai ola, M. Lions, N. Ranjba -Sah aie, M. Me moux, L. Dubau, A.
Zi olo, F. Jaouen, F. Mailla d, ACS Ca al. 2018, 8, 11264-11276.
134 H. Zhang, X. Gu, P. Liu, J. Song, J. Cheng, H. Su, J. Ma e . Chem. A. 2017, 5,
2288-2296.
135 A. M. Nau h, E. Schech el, R. Dö en, W. T emel, T. Opa z, J. Am. Chem. Soc. 2018,
140, 14169-14177.
136 C. Ce ezo-Na a e e, I. Mus ieles Ma in, H. Ga cía-Miquel, A. Co ma, B.
Chaud e , L. M. Ma ínez-P ie o, ACS Ca al. 2022, 12, 8462-8475.
137 A. M. López-Vinasco, L. M. Ma ínez-P ie o, J. M. Asensio, P. Lecan e, B.
Chaud e , J. Cámpo a, P. W. N. M. an Leeuwen, Ca al. Sci. Technol. 2020, 10, 342-
350.
138 Nanopa icles in Ca alysis: Ad ances in Syn hesis and Applica ions, K. Philippo
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139 P. La a, A. Suá ez, V. Colliè e, K. Philippo , B. Chaud e , ChemCa Chem 2014, 6,
87-90.
140 S. Renghausen, C. Van S appen, N. Le in, S. T ica d, K. L. Luska, S. DeBee , B.
Chaud e , A. Bo de , W. Lei ne , Small 2021, 17, 2006683.
141 A. M. T zeciak, A.W. Augus yniak, Coo d. Chem. Re . 2019, 384, 1-20.
142 P. Wójcik, M. Ma , S. Ulukanli, A. M. T zeciak, RSC Ad . 2016, 6, 36491-36499.
143 D. O. Sil a, J. D. Schol en, M. A. Gelesky, S. R. Teixei a, A. C. B. Dos San os, E.
F. Souza-Aguia , J. Dupon , ChemSusChem 2008, 1, 291-294.
144 L. C. Mo aes, R. C. Figuei edo, J. P. Espinós, F. Va ie , A. F ancone i, C. Jaime,
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145 M. Kidonakis, M. S a akis, ACS Ca al. 2018, 8, 1227-1230.

Chap e II:
Objec i es
Chap e II ou lines he main goals o his PhD hesis, ocusing on he e icien
design o nanoca alys s ailo ed o op imise hei ca aly ic pe o mance in key
chemical ans o ma ions.
Objec i es
O e he pas ew decades, signi ican ad ances in nanoscience ha e ocused
on con olling he cha ac e is ics o a wide ange o nanoma e ials based on hei
po en ial applica ions. In he case o me al nanopa icles, hese cha ac e is ics (such
as composi ion, size, and su ace p ope ies) a e c ucial ac o s ha in luence hei
eac i i y and, consequen ly, hei ca aly ic beha iou . De eloping new syn he ic
me hodologies ha enable p ecise con ol o e hese pa ame e s is c ucial o
unde s anding and p edic ing hei po en ial applica ions. The backbone o his PhD
hesis can be summa ised by he ollowing speci ic objec i es:
1. Syn hesis o di e en ligands ha can se e as s abilising agen s o
nanopa icles: SNS pince - ype ligands, imidazole-2-ylidenes (IP and
IMes) and 1,2,3- iazolylidenes (MIC).
2. Syn hesis o u henium nanopa icles s abilised by SNS ligands using he
o ganome allic me hod, ollowed by an in es iga ion o hei s uc u al
and mo phological cha ac e is ics.
3. Ca aly ic ac i i y s udy o u henium nanopa icles s abilised wi h SNS
pince ligands in he educ ion o ni ous oxide using hyd osilanes.
4. Syn hesis o i on, cobal and nickel nanopa icles s abilised wi h uNHC
ligands using he o ganome allic app oach. This in ol es examining hei
s uc u al and mo phological cha ac e is ics and analysing he di e ences
among he h ee me als when s abilised by he same ligands.
5. Tes ing he ca aly ic ac i i y o i s ow ansi ion me al nanopa icles in
he me hanolysis o H3N·BH3, a p omising p ocess o hyd ogen
gene a ion.
6. Syn hesis o u henium and nickel nanopa icles s abilised by MIC
ligands employing he o ganome allic me hod, ollowed by hei
cha ac e isa ion using con en ional solid-s a e echniques.
7. Assessmen o he ca aly ic ac i i y o hese nanopa icles in
hyd ogen/deu e ium (H/D) exchange eac ions using hyd osilanes and
ela ed hyd ides om main g oup elemen s as no el subs a es o he
p ocess.
55

Ru·SNS nanopa icles
63
3.1 In oduc ion
S-con aining pince - ype ligands, such as SNS and SNN, a e an easily
accessible a ie y o ligands, al hough hey ha e no ecei ed as much a en ion as
o he pince sys ems. In pa icula , SNS ligands a e cha ac e ised by a sulphu -
ni ogen-sulphu a angemen , which ea u es h ee a oms wi h a ailable elec on lone
pai s. This enhances hei abili y o ac as Lewis bases, a aching o Lewis acidic me al
cen es and allowing hem o unc ion as iden a e pince ligands due o hei
mul iden a e s uc u e.1,2 As a esul o hei e sa ile applica ions and obus chela ing
abili y, pince - ype ligands ha e become essen ial componen s o o ganome allic
chemis y. They play a non-innocen ole in some ca aly ic p ocesses.3,4 Figu e 1
illus a es wo examples o u henium SNS complexes epo ed in he li e a u e by
Guse e al. and Zimme man, Wasse e al. Guse ’s complex has been used as ca alys
in he hyd ogena ion o a ious unsa u a ed compounds, such as es e s, ke ones, and
aldehydes.5 Simila ly, Zimme man’s complexes ha e been u ilised bo h in he
hyd ogena ion o es e s and he o ma ion o amides (Figu e 1).6
Figu e 1. Examples o RuSNS complexes epo ed in he li e a u e.
1 A. Khanzadeh, Ligand-Assis ed Ca alysis Using Me al SNS Complexes, PhD Thesis,
Uni e si y o O awa, 2023.
2 H. G. Sogukome ogulla i, S. P. Yalçin, U. Cylan, E. Ay a , M. Aygün, D. S. Richeson, M.
Sönmez, J. Chem. Sci. 2019, 131, 32.
3 V. Singh, R. Singh, A. S. Haza i, D. Adhika i, JACS Au 2023, 3, 1213-1220.
4 K. E. Rosenkoe e , M. K. Wojna , B. J. Cha e e, J. W. Zille , A. F. Heyduk, Ino g. Chem.
2018, 57, 9728-9737.
5 D. Spasyuk, S. Smi h, D. G. Guse , Angew. Chem. In . Ed. 2013, 52, 2538-2542.
6 J. Schö genhume , A. Zimme mann, M. Wase , O g. P ocess Res. De . 2018, 22, 862-870.
Chap e III
64
In addi ion o hese simple alipha ic ligand sys ems, py idine-based SNS
complexes ha e also been desc ibed by Zimme mann, Wase e al. o hyd ogena ion
and dehyd ogena ion eac ions (Figu e 2).6
Figu e 2. Examples o py idine-based RuSNS complexes epo ed in he li e a u e.
The excep ional ca aly ic pe o mance exhibi ed by pince u henium
complexes in a ious hyd ogena ion eac ions has been also ex ended o he
hyd ogena ion o ni ous oxide. This chemical emedia ion me hod in ol es he
con e sion o ni ous oxide in o benign ni ogen gas and wa e .7
Ni ous oxide (N2O) is a po en g eenhouse gas whose a mosphe ic
concen a ion has signi ican ly inc eased since he beginning o he indus ial e a.
While his gas is p oduced bo h by an h opogenic and na u al sou ces, an h opogenic
emissions ha e isen abou 30% in jus ou decades.8 Among he models used o
compa e he clima e impac o di e en gases, he mos common is Global Wa ming
Po en ial (GWP), which is indexed pe uni o mass o CO2. Acco ding o i s GWP,
each uni o mass o N2O is equi alen o nea ly 300 uni s o ca bon dioxide,9 making
he decomposi ion o ni ous oxide an impo an a ea o esea ch. In he con ex o a
7 R. Zeng, M. Felle , Y. Ben-Da id, D. Mils ein, J. Am. Chem. Soc. 2017, 139, 5720-5723.
8 H. Tian, R. Xian, J.G. Canadell e al., Na u e 2020, 586, 248-256.
9 G.A. Meehl, T.F. S ocke , W.D. Collins, P. F iedlings ein, A.T. Gaye, J.M. G ego y, A. Ki oh,
R. Knu i, J.M. Mu phy, A. Noda, S.C.B. Rape , I.G. Wa e son, A.J. Wea e and Z.-C. Zhao
in Clima e Change 2007: The Physical Science Basis. Con ibu ion o Wo king G oup I o he
Fou h Assessmen Repo o he In e go e nmen al Panel on Clima e Change, Solomon, S.,
D. Qin, M. Manning, Z. Chen, M. Ma quis, K.B. A e y , M. Tigno and H.L. Mille (Eds.),
Camb idge Uni e si y P ess, 2007.
Ru·SNS nanopa icles
65
ci cula economy, ans o ming N2O in o ha mless N2 se es no only o educe i s
p esence in he a mosphe e bu also o alo ise i in o o he chemicals.10,11
Va ious homogeneous and he e ogeneous ca alys s ha e been employed o
ac i a e and educe ni ous oxide, eleasing ni ogen gas in he p ocess.12-15 This
ac i a ion can be achie ed di ec ly wi h educing agen s such as H2. The
hyd ogena ion o N2O appea s o be a p omising me hod o educing ni ous oxide,
p oducing bo h N2 and H2O.7,16 Bo anes ha e also been used as educ an s in oxygen
ans e eac ions om ni ous oxide, using 1s ow ansi ion me al complexes as
ca alys s.17 Gene ally, in mos epo ed p eceden s, N2O educ ion occu s h ough
ans e ence o he oxygen a om o an accep o such as hyd ogen, phosphines,
bo anes, hyd oca bons, o silanes.18
As an al e na i e o educ ion by hyd ogen, silanes a e commonly employed
as educing agen s in a a ie y o p ocesses, including he educ ion o ca bonyl
compounds, alkyne hyd osilyla ion, and he ac i a ion o small molecules like
CO2.19,20,21 Some ad an ages o using silanes include hei low cos and ease o
handling. Howe e , he e a e ew p eceden s o hei use as educ an s o ni ous
oxide.
10 B. A yal, R. Gu ung, A. F. Cama go, G. Fonga o, H. T eichel, B. Mainali, M. J. Ango e, H.
H. Ngo, W. Guo, S. R. Puadel, En i on. Pollu . 2022, 314, 120272-120288.
11 K. Se e in, Chem. Soc. Re . 2015, 44, 6375-6386.
12 Y. Pang, M. Leu zsch, N. Nö hling, J. Co nella, J. Am. Chem. Soc. 2020, 142, 19473-19479.
13 R. Zeng, M. Felle , Y. Diskin-Posne , L. J. W. Shimon, Y. Ben-Da id, D. Mils ein, J. Am.
Chem. Soc. 2018, 140, 7061-7064.
14 V. R. Landae a, R. E. Rod íguez-Lugo, Ino g. Chim. Ac a 2015, 431, 21-47.
15 D. J. Xiao, E. D. Bloch, J. A. Mason, W. L. Queen, M. R. Hudson, N. Planas, J. Bo ycz, A.
L. Dzubak, P. Ve ma, K. Lee, F. Bonino, V. C ocellà, J. Yano, S. Bo diga, D. G. T uhla , L.
Gaglia di, C. M. B own, J. R. Long, Na u e Chem. 2014, 6, 590-595.
16 I. O ega-Lepe, P. Sánchez, L. L. San os, P. La a, N. Rendón, J. López-Se ano, V. Salaza -
Pe eda, E. Ál a ez, M. Paneque, A. Suá ez, Ino g. Chem. 2022, 61, 18590-18600.
17 X. Chen, H. Wang, S. Du, M. D iess, Z. Mo, Angew. Chem., In . Ed. 2022, 61, e202114598.
18 J. Bösken, R. E. Rod íguez-Lugo, S. Nappen, M. T incado, H. G ü zmache , Chem. Eu . J.
2023, 29, e202203632, 1-8.
19 B. M. T os , Z. T. Ball, J. Am. Chem. Soc. 2005, 127, 17644-17655.
20 R. A. P amudi a, K. Mo oku a, ChemSusChem 2021, 14, 281-292.
21 Y. Nagai, O g. P ep. P oced. In . 1980, 12, 13-48.
Chap e III
66
Mils ein e al. published one o he mos in e es ing ecen s udies in his a ea
in 2017.7 In hei esea ch, he au ho s desc ibed a RuPNP pince complex capable o
educing N2O wi h di e en hyd osilanes (Me2PhSiH, MePh2SiH, and BuMe2SiH)
unde mild condi ions o ca alys load, p essu e and empe a u e, as summa ised in
Scheme 1.
Scheme 1. Ni ous oxide educ ion by hyd osilanes ca alysed by a RuPNP pince
complex.
The abili y o disilanes o pe o m he same p ocess was ecen ly desc ibed
by Can a e al. (Scheme 2),22 making he i s me al- ee example o N2O educ ion
unde mild condi ions.
Scheme 2. Me al- ee educ ion o ni ous oxide.
As N2O is an indus ial byp oduc , his educ ion p ocess could help elimina e
i om he a mosphe e, while also a oiding he use o H2O2 o O2 o silane
22 L. An ho e-Dalion, E. Nicolas, T. Can a , ACS Ca al. 2019, 9, 11563-11567.
Ru·SNS nanopa icles
67
oxida ion.23 I is impo an o no e ha oxida ion o silanes wi h N2O leads o he
o ma ion o de i a i es con aining Si—O bonds (namely silanols and siloxanes),
which a e ele an o he syn hesis o di e en silicon-based polyme ic
ma e ials.24,25,26
Gi en he abili y o ansi ion me al nanopa icles o ca alyse σ‑Si—H bond
ac i a ion eac ions, and he eac i i y o u henium ca alys s wi h N2O and p e iously
men ioned silanes, he e a e compelling easons o explo e he educ ion o ni ous
oxide wi h hyd osilanes ca alysed by u henium nanopa icles.27
To he bes o ou knowledge, he e is no p eceden o he use o SNS ligands
as s abilising agen s o ansi ion me al nanopa icles.
Chap e III o his PhD hesis ocuses on he p epa a ion o u henium
nanopa icles s abilised by SNS ligands and he in es iga ion o hei ca aly ic
pe o mance in he educ ion o N2O wi h hyd osilanes.
3.2 Resul s and Discussion
3.2.1 SNS ligands as s abilising agen s o Ru nanopa icles
Fou di e en SNS ligands ha e been syn hesised o be used as s abilising
agen s o u henium nanopa icles.28 Speci ically, SNS ligands de i ed om
seconda y (SNS1 and SNS2, Scheme 3) o a oma ic (SNS3 and SNS4, Scheme 4)
amine, con aining alkyl (SNS1, SNS3) o a yl (SNS2, SNS4) subs i uen s on he
sulphu a om, ha e been p epa ed wi h low o mode a e yields ollowing a p ocedu e
epo ed in he li e a u e and de ailed in he expe imen al sec ion. These ligands ha e
been isola ed as ligh -colou ed solids o oils, wi h yields anging om 10 o 82 %.
Due o he mul iden a e s uc u e o SNS ligands, pince - ype beha iou has been
23 H. H. Mo e o, M. Schulze, G. Wagne , in Silicones. Ullmann’s Encyclopedia o Indus ial
Chemis y, 32, 675-708. Weinheim: Wiley-VCH, 2012.
24 R. Mu uga el, A. Voig , M. G. Walawalka , H. W. Roesky, Chem. Re . 1996, 96, 2205-2236.
25 S. E. Denma k, C. S. Regens, Acc. Chem. Res. 2008, 41, 1486-1499.
26 Y. Abe, T. Gunji, P og. Polym. Sci. 2004, 29, 149-182.
27 J. M. Asensio, D. Bouzoui a, P. W. N. M. an Leeuwen, B. Chaud e , Chem. Re . 2020, 120,
1042-1084.
28 P. Molinillo, B. Lac oix, F. Va ie , N. Rendón, A. Suá ez, P. La a, Chem. Commun. 2022,
58, 7176-7179.

Chap e III
68
p e iously obse ed in RuSNS complexes,6 so, in p inciple, simila p ope ies migh
be an icipa ed o Ru∙SNS nanopa icles.
Scheme 3. Syn hesis o SNS1 and SNS2 ligands.
Scheme 4. Syn hesis o SNS3 and SNS4 ligands.
3.2.2 Syn hesis and cha ac e isa ion o Ru∙SNS nanopa icles
Ru henium nanopa icles s abilised by SNS ligands we e p epa ed ollowing
he o ganome allic app oach.29 A solu ion o he ole inic complex [Ru(COD)(COT)]
(COD= 1,5 cyclooc adiene, COT = 1,3,5-cyclooc a iene) in THF was decomposed a
oom empe a u e unde 3 ba o H2 in he p esence o non-s oichiome ic amoun s
(0.2 o 0.5 equi .) o an SNS ligand (Scheme 5); u he de ails can be ound in he
expe imen al sec ion.
Scheme 5. Syn hesis o u henium nanopa icles s abilised by SNS1-4 ligands.
29 K. Philippo , B. Chaud e , in Comp ehensi e O ganome allic Chemis y III, R. H. C ab ee
& M. P. Mingos (Eds-in-Chie ); Applica ions III: Func ional Ma e ials, En i onmen al and
Biological Applica ions, D. O´Ha e (Volume Ed.), Vol 12, Chap e 03, 71-99, Else ie , 2007.
Ru·SNS nanopa icles
69
A e 30 min. o eac ion, he colou o he sys em changed om he ini ial
yellow o da k b own. The eac ion mix u e was s i ed o e nigh , and he pa icles
we e hen p ecipi a ed and washed wi h pen ane o emo e he uncoo dina ed ligand.
Di e en ligand/me al a ios we e employed, esul ing in he syn hesis o i e
colloids. Fou o hem we e p epa ed using 0.5 equi . o SNS1-4, while he las one
was p epa ed using 0.2 equi . o SNS4. All samples we e cha ac e ised by TEM
(Figu e 2-Figu e 7, Table 1) and ICP (Table 1), e ealing me al con en s anging om
32 o 81%w . In all cases, mainly small and well-dispe sed nanopa icles (Figu e 2-
Figu e 7) we e ob ained, wi h mean sizes be ween 1.5 and 2.3 nm. The use o lowe
amoun s o SNS1-3 ligands (0.2 equi .) esul ed in he o ma ion o bulk me al, while
o SNS4, sligh agglome a ion was obse ed (Figu e 7). As p e iously no ed,
inc easing he ligand/me al a io led o a dec ease in he mean size o he
nanopa icles.30
200
150
100
50
0
0 1 2 3
Mean size (nm)
Figu e 2. TEM image wi h size dis ibu ion his og am o Ru⋅SNS10.5.
30 P. La a, O. Ri ada-Wheelaghan, S. Coneje o, R. Po eau, K. Phlippo , B. Chaud e , Angew.
Chem., In . Ed. 2011, 50, 12080-12084.
d = 1.5 (0.2) nm
Numbe o Nanopa icles
Chap e III
70
200
150
100
50
0
0 1 2 3 4
Mean size (nm)
Figu e 3. TEM image wi h size dis ibu ion his og am o Ru⋅SNS20.5.
200
150
100
50
0
0 1 2 3
Mean size (nm)
Figu e 4. TEM image wi h size dis ibu ion his og am o Ru⋅SNS30.5.
200
150
100
50
0
0 1 2 3 4
Mean size (nm)
Figu e 5. TEM image wi h size dis ibu ion his og am o Ru⋅SNS40.5.
d = 1.9 (0.4) nm
d = 1.5 (0.2) nm
d = 1.6 (0.2) nm
Numbe o Nanopa icles
Numbe o Nanopa icles
Numbe o Nanopa icles
Ru·SNS nanopa icles
71
200
150
100
50
0
0 1 2 3 4
Mean size (nm)
Figu e 6. TEM image wi h size dis ibu ion his og am o Ru⋅SNS40.2.
Figu e 7. TEM image o Ru⋅SNS40.2, showing agglome a ed NPs.
Table 1. Analysis o Ru·SNS nanopa icles by TEM and ICP.
Colloid
L/Ru a io
%w Ru
Mean size (nm)
Ru⋅SNS10.5
0.5
41
1.5 (0.2)
Ru⋅SNS20.5
0.5
32
1.9 (0.4)
Ru⋅SNS30.5
0.5
41
1.5 (0.2)
Ru⋅SNS40.5
0.5
47
1.6 (0.2)
Ru⋅SNS40.2
0.2
81
2.3 (0.4)
The c ys alline cha ac e o he Ru∙SNS nanopa icles was con i med by High
Resolu ion T ansmission Elec on Mic oscopy (HRTEM) measu emen s conduc ed
d = 2.3 (0.4) nm
Numbe o Nanopa icles
Chap e III
78
Fi s , a s udy o he ca aly ic pe o mance o Ru·SNS nanopa icles in he
educ ion o N2O wi h dime hylphenylsilane (PhMe2SiH, 1a) e ealed he o ma ion
o wo p oduc s: silanol (2a) and siloxane (3a) (Scheme 7). Gi en he signi icance o
Si—O con aining molecules in he syn hesis o silicon-based ma e ials, bo h p oduc s
a e o in e es , pa icula ly siloxane (3a) due o i s abili y o p oducing polyme ic
ma e ials.38
Scheme 7. Reduc ion o N2O wi h PhMe2SiH (1a) ca alysed by Ru·SNS
nanopa icles.
Ini ial expe imen s we e pe o med wi h Ru⋅SNS10.5, using 1.0 mol% o Ru
unde 1 ba o N2O a 55 ºC, wi h PhMe2SiH as model subs a e. Con e sion and
selec i i y we e de e mined by 1H NMR spec oscopy, using mesi ylene as an in e nal
s anda d. Unde hese eac ion condi ions, a con e sion o 76% was obse ed,
yielding a mix u e o silanol (2a) and siloxane (3a) wi h a 40:60 a io (Table 6, en y
1). A e con i ming ha Ru·SNS nanopa icles we e ac i e o his p ocess, he
ca aly ic pe o mance o he o he ou ca alys s was examined. Table 6 summa ises
he con e sion and selec i i y alues o all he colloids. Excep o Ru⋅SNS10.5, all
ca alys s p epa ed wi h 0.5 equi . o ligand (Ru⋅SNS20.5, Ru⋅SNS30.5 and Ru⋅SNS40.5)
showed con e sion alues g ea e han 99% and silanol:siloxane a ios anging
be ween 12:88 and 25:75, whe e siloxane (3a) was he dominan p oduc (Table 6).
These ca aly ic esul s align wi h he expec a ions o ca alys s wi h a compa able
numbe o ac i e si es, as in e ed om he numbe o su ace a oms (53-63%, Table
5). I is also no ewo hy ha he syn he ic p ecu so [Ru(COD)(COT)] p o ided a e y
low silane con e sion, less han 5% (see below).
38 S. Ananda Kuma , M. Alaga , M. Mandhakini in Concise Encyclopedia o High Pe o mance
Silicones, Chap e 3, 39-45, J. P. Lewicki, R. S. Maxwell (Eds), Wiley, 2014.

Ru·SNS nanopa icles
79
Table 6. Reduc ion o N2O wi h PhMe2SiH using Ru·SNS nanopa icles.
En y
Ca alys
Con e sion (%)
2a:3a a io
1
Ru⋅SNS10.5
76
40:60
2
Ru⋅SNS20.5
>99
12:88
3
Ru⋅SNS30.5
>99
25:75
4
Ru⋅SNS40.5
>99
20:80
5
Ru⋅SNS40.2
28
50:50
Al hough all ca alys s p epa ed wi h Ru/SNS a io o 0.5 (en ies 1-4) showed
high con e sion alues, he ac i i y dec eased o Ru⋅SNS40.2 (en y 5), likely due o
he p esence o a sligh me al agglome a ion in ha sample obse ed by TEM analysis
(Figu e 7). These me al agglome a es may hinde he ca aly ic ac i i y o his colloid,
leading o a lowe con e sion alue. Among all he 0.5 equi . ca alys s, Ru⋅SNS10.5
showed he lowes con e sion (76%), consis en wi h a highe deg ee o su ace
co e age o Ru⋅SNS10.5 compa ed o Ru⋅SNS20.5, as in e ed om hei XPS analyses
(Table 2).
To de e mine he selec i i y o he ca aly ic p ocess, he wo p oduc s 2a and
3a we e sepa a ed by lash ch oma og aphy on silica gel using pen ane →
pen ane/E 2O (1:1) as eluen . Each pu e p oduc was hen analysed, allowing o
iden i ica ion, by HRMS and 1H NMR spec oscopy. As men ioned ea lie , o all he
Ru·SNS0.5 ca alys s, siloxane was he main p oduc , wi h silanol p esen ed in smalle
quan i ies (Figu e 13). A e ca alysis, TEM measu emen s o Ru⋅SNS40.5 colloid,
ob ained by deposi ing a d op o he c ude eac ion mix u e on a coppe g id,
con i med ha he pa icle size emains p ac ically unchanged. Figu e 14 shows a
TEM image wi h size dis ibu ion his og am a e he ca aly ic p ocess (mean size 1.5
(0.3) nm).
Chap e III
80
Figu e 13. 1H NMR spec um (CD2Cl2, 400 MHz) o he c ude eac ion mix u e
a e he educ ion o N2O wi h PhMe2SiH using Ru⋅SNS20.5 nanopa icles as
ca alys (* deno es mesi ylene employed as in e nal s anda d and # deno es esidual
CH2Cl2).
150
100
50
0
0 1 2 3
Mean size (nm)
Figu e 14. TEM image wi h size dis ibu ion his og am o Ru⋅SNS40.5 a e
he ca aly ic eac ion.
d = 1.5 (0.3) nm
Numbe o Nanopa icles
Ru·SNS nanopa icles
81
To explo e he scope o he ca aly ic p ocess, a ious hyd osilanes we e es ed
as educ an s, using he Ru⋅SNS40.5 colloid as a ep esen a i e ca alys (Table 7).
Table 7. Reduc ion o N2O wi h hyd osilanes using Ru⋅SNS40.5.
En y
Hyd osilane
Con e sion (%)
Silanol:Siloxane a io
1
Ph
2
MeSiH (1b)
>99
>99:1
2a
(PhCH
2
CH
2
)Me
2
SiH (1c)
98
>1:99
3
nP
3
SiH (1d)
95
58:42
4
iP
3
SiH (1e)
0
---
5
(E O)
3
SiH (1 )
98
63:37
Reac ion condi ions, unless o he wise no ed: 1.0 mol% Ru, 1 ba N2O, 65 ºC, THF,
eac ion ime: 24 h. aReac ion ime: 48 h.
Comple e silane con e sion and high selec i i y owa ds he o ma ion o
silanol 2b we e obse ed when me hyldiphenylsilane (1b) was used as he educ an
(en y 1). In con as , he use o dime hylphene ylsilane (1c), led p ima ily o he
o ma ion o siloxane 3c wi h >99% selec i i y (en y 2). Fu he mo e, high
con e sions we e also achie ed wi h ip opylsilane (1d) and ie hoxysilane (1 ), wi h
silanol:siloxane a ios o app oxima ely 6:4 (en ies 3 and 5, espec i ely). Howe e ,
no con e sion was obse ed o iisop opylsilane (1e), likely due o s e ic hind ance
(en y 4). All p oduc s ha e been ully cha ac e ised by NMR spec oscopy and
HRMS (see he Expe imen al Sec ion). Figu e 15 and 16 show he 1H NMR and
13C{1H} NMR spec a, espec i ely, o dime hylphene ylsiloxane (3c) as a
ep esen a i e example o he cha ac e isa ion pe o med o each p oduc .
Chap e III
82
Figu e 15. 1H NMR spec um (CD2Cl2, 400 MHz) o [(PhCH2CH2)Me2Si]2O (3c)
(# deno es esidual CH2Cl2).
Figu e 16. 13C{1H} NMR spec um (CD2Cl2, 101 MHz) o [(PhCH2CH2)Me2Si]2O
(3c) (# deno es esidual CD2Cl2).
Ru·SNS nanopa icles
83
To gain u he insigh in o he ans o ma ion o hyd osilanes in o silanols
and siloxanes, a se ies o con ol expe imen s we e pe o med.
Fi s , he o ma ion o N2 om N2O was de ec ed by GC-MS analysis o he
headspace gas in he Fische Po e eac o a e he ca aly ic educ ion o N2O wi h
dime hylphenylsilane using Ru·SNS40.5 (see Expe imen al Sec ion).
Nex , as al eady no ed, he o ganome allic p ecu so [Ru(COD)(COT)] was
es ed as a ca alys in he educ ion o ni ous oxide wi h dime hylphenylsilane, unde
he same eac ion condi ions as hose used o Ru·SNS nanopa icles (THF, 55 ºC, 1
ba N2O, 1 mol% Ru). 1H NMR analysis e ealed a e y low silane con e sion (below
5%) (see Expe imen al Sec ion), in s a k con as o he highe ac i i y obse ed o
he nanopa icles (Table 6).
Ano he expe imen , a me cu y poisoning es , was ca ied ou o de e mine
whe he he ca aly ic p ocess was occu ing due o he p esence o molecula species
o u henium.39 This es was ca ied ou in he educ ion o N2O wi h PhMe2SiH using
Ru⋅SNS40.5, wi h he addi ion o 0.1 mmol o Hg o he eac ion mix u e. 1H NMR
analysis o he eac ion mix u e a e 24 hou s shows ha he con e sion d opped o
30%, (Figu e 17), a alue conside ably lowe han he con e sion obse ed wi h he
non-poisoned ca alys (>99), and, in addi ion, siloxane was he only p oduc de ec ed.
These con ol expe imen s p o ided aluable insigh s in o he ca aly ic sys em.
Fi s , he eac ion did no occu in he absence o a sui able ca alys . Second, since
he me al oxida ion s a e is he same in bo h he o ganome allic p ecu so and
Ru·SNS NPs, Ru(0), he na u e o he ca alys is c i ical o he ac i a ion o he N2O
molecule. Finally, he possibili y o ca alysis being pe o med by well-de ined
u henium complexes canno be uled ou .
Fu he mo e, in o de o in es iga e he eac ion mechanism o he p ocess
conduc ing o he o ma ion o siloxane, a se ies o expe imen s we e ca ied ou o
es a ious hypo heses, which a e desc ibed in he nex pages.
39 I. C. Chagunda, T. Fishe , M. Schie ling, J. S. McIndoe, O ganome allics 2023, 42, 2938-
2945.

Chap e III
84
Figu e 17. 1H NMR spec um (CD2Cl2, 300 MHz) a e he educ ion o N2O wi h
PhMe2SiH using Ru·SNS40.5 in he p esence o Hg. (* deno es mesi ylene added as
he in e nal s anda d, # deno es esidual CH2Cl2, and + deno es esidual H2O).
Fo ma ion o siloxane h ough he oxida ion o disilane
The o ma ion o siloxanes could in ol e he oxida ion o disilanes, which a e
o med h ough he dehyd ogena i e coupling o eac ed hyd osilanes.40 To
in es iga e his possibili y, he disilane PhMe2SiSiMe2Ph was eac ed wi h N2O
employing Ru⋅SNS40.5 as ca alys (THF-d8, 55 ºC, 1 ba N2O, 1 mol% Ru, 24 h).
Howe e , no eac ion was obse ed unde hese condi ions and his hypo hesis was
uled ou (Scheme 8).
Scheme 8. Con ol expe imen o he o ma ion o he siloxane 3a om disilane.
40 F. Neumeye , N. Aune , Chem. Eu . J. 2016, 22, 17165-17168.
Ru·SNS nanopa icles
85
Fo ma ion o siloxane ia silanol-silanol condensa ion
The o ma ion o he siloxane 3a could occu h ough he condensa ion o wo
silanol molecules ia dehyd a ion (Scheme 9).41 Howe e , no con e sion was
obse ed, no wa e was de ec ed by 1H NMR when a solu ion o comme cial 2a in
d y THF was hea ed o 55 ºC o 24 h in he p esence o Ru·SNS40.5. The e o e, his
mechanism was also disca ded.
Scheme 9. Con ol expe imen o he o ma ion o he siloxane 3a by silanol
dehyd a ion.
Fo ma ion o siloxane ia silanol-silane dehyd ogena ion
The inal possibili y conside ed in ol ed a dehyd ogena i e coupling o
silane and silanol. Unde he ca aly ic condi ions p e iously p oposed, his mechanism
would equi e he ini ial o ma ion o a silanol molecule om he silane, ollowed by
he coupling o silanol and silane o o m a siloxane. To es his hypo hesis, he
eac ion o silane 1a wi h silanol 2a was pe o med unde he same eac ion condi ions
(Scheme 10) esul ing in 100% con e sion o he siloxane 3a and hyd ogen o ma ion,
as con i med by 1H NMR spec oscopy (Figu e 18).
Scheme 10. Con ol eac ion o he o ma ion o he siloxane 3a by
dehyd ogena i e coupling o silanol and silane.
41 W. T. G ubb, J. Am. Chem. Soc. 1954, 76, 3408-3414.
Chap e III
86
I is wo h no ing ha he eac ion was pe o med in a Fishe -Po e eac o ,
which esul ed in a sligh inc ease in p essu e, a ibu ed o he e olu ion o hyd ogen
gas. All hese obse a ions suppo a mechanism o he educ ion o ni ous oxide
wi h hyd osilanes, ca alysed by Ru·SNS NPs, in ol ing he ini ial oxida ion o silane
o silanol, he o ma ion o ni ogen gas, and subsequen coupling o he silanol wi h
a second molecule o hyd osilane. This eac ion eleases H2 and p oduces he siloxane
de i a i e.
Figu e 18. 1H NMR spec a (THF-d8, 400 MHz) o he con ol expe imen o he
o ma ion o he siloxane 3a by dehyd ogena i e coupling o silanol and silane. (*
deno es mesi ylene added as he in e nal s anda d).
3.3 Expe imen al Sec ion
3.3.1 Gene al conside a ions
All expe imen al p ocedu es we e pe o med unde ni ogen o a gon
a mosphe e employing s anda d Schlenk echniques, Fishe -Po e ubes echniques,
o a B aun MB aun Ubilab P o glo ebox. The sol en s used (THF, pen ane, die hyl
e he ) we e ea ed wi h an app op ia e desiccan (sodium benzophenone-ke yl in he
case o THF and die hyl e he , sodium in he case o pen ane) and dis illed unde ine
Ru·SNS nanopa icles
87
a mosphe e p io o hei use. The p ecu so [Ru(COD)(COT)] (COD= 1,5
cyclooc adiene, COT = 1,3,5-cyclooc a iene),42 dime hylphene ylsilane,43 and SNS
ligands6 we e syn hesised acco ding o me hodologies desc ibed p e iously in he
li e a u e. Hyd ogen gas (99.99%) was pu chased om Ai Liquide and all o he
chemicals we e used as ecei ed om he comme cial supplie Sigma-Ald ich.
T ansmission Elec on Mic oscopy (TEM) measu emen s we e pe o med
using a Philips CM200 and a FEI TALOS F200S wo king a 200 kV in he “Cen o
de In es igación, Tecnología e Inno ación - CITIUS” (Uni e sidad de Se illa). The
de e mina ion o he pa icle mean size was ca ied ou by measu ing app oxima ely
h ee hund ed indi idual nanopa icles, and he s a is ical ea men o he
measu emen s was pe o med using ImageJ and O igin, so wa es commonly
employed in he li e a u e.44 The samples o mic oscopy ha e been p epa ed by
deposi ing a d op o he nanopa icle dispe sion in THF on o a coppe g id and
allowing i o d y in ai . The c ys al s uc u es o he pa icles we e also elucida ed
using High Resolu ion T ansmission Elec on Mic oscopy (HRTEM) and Scanning
T ansmission Elec on Mic oscopy simul aneously wi h Ene gy Dispe si e X-Ray
Spec oscopy (STEM-EDX). In he case o HRTEM, an ABSF il e was applied o
enhance con as and educe noise.45 Va ious u henium nanopa icles we e scanned
o e alua e hei composi ion by STEM-EDX. A small elec on p obe (size a ound 0.5
nm, in ensi y abou 500 pA) was s udied inside an a ea o 140x160 pixels, wi h a dwell
ime o 50 µs/pixel. The EDX signal was in eg a ed o e abou 200 ames. These
measu emen s we e ca ied ou by D . Be and Lac oix om he “T ibología y
P o ección de Supe icies” g oup a he depa men o “Física Aplicada I”
(Uni e sidad de Se illa).
NMR expe imen s we e eco ded a 25 ºC on B uke DRX-500, DRX-400,
and DRX-300 spec ome e s. The 1H and 13C spec a we e e e enced o ex e nal
42 P. Pe ici, G. Vi ulli, Ino g. Syn . 1983, 22, 176-181.
43 M. I o, M. I azaki, T. Abe, H. Nakazawa, Chem. Le . 2016, 45, 1434-1436.
44 S. Zhang, C. Wang, Me hods P o oc. 2023, 6, 63-68.
45 R. Kilaas, J. Mic osc. 1998, 190, 45-51.
Chap e III
94
Figu e 19. N2 de e mina ion by GC-MS: a) N2O con ol expe imen ; b) N2 con ol
expe imen ; c) ca aly ic eac ion (Table 6, en y 4).
[Ru(COD)(COT)] ca alysis
In a glo ebox, 0.3 mL o a eshly p epa ed suspension o [Ru(COD)(COT)]
(7.5 µmol) in THF and 0.2 mL o a THF solu ion o dime hylphenylsilane (115 µL,
0.75 mmol) we e in oduced in o a Fishe -Po e essel. The ni ogen a mosphe e was
eplaced by 1 ba o ni ous oxide. The eac ion mix u e was s i ed a 55 ºC o 24 h.
A e his pe iod o ime, he eac ion c ude was analysed by 1H NMR, e ealing a
con e sion lowe han 5% (Figu e 20).

Ru·SNS nanopa icles
95
Figu e 20. 1H NMR spec um (CD2Cl2, 300 MHz) a e he educ ion o N2O wi h
PhMe2SiH using [Ru(COD)(COT)]. (* deno es mesi ylene added as he in e nal
s anda d and # deno es esidual CH2Cl2).
Hg es
The s anda d p ocedu e was epea ed wi h he addi ion o Hg (20 mg, 0.1
mmol) o he eac ion mix u e, employing Ru⋅SNS40.5 as ca alys (7.5 µmol Ru) and
Me2PhSiH as subs a e (115 µL, 0.75 mmol). In his case, he con e sion dec eased
om >99% o 30%.
Fo ma ion o siloxane ia he oxida ion o disilane.
In a glo ebox, 0.2 mL o a THF-d8 solu ion con aining disilane
PhMe2SiSiMe2Ph (223 µL, 0.75 mmol) and 0.3 mL o a THF-d8 suspension o
Ru⋅SNS40.5 (7.5 µmol) we e in oduced in o a Fishe -Po e essel, which was loaded
wi h 1 ba o N2O and hea ed a 55 ºC o 24 h. A e ha pe iod, 1H NMR analysis o
he eac ion c ude e ealed he absence o siloxane o any o he eac ion p oduc .
Chap e III
96
Fo ma ion o siloxane ia condensa ion o silanol-silanol.
In a glo ebox, 0.2 mL o a THF-d8 solu ion con aining comme cial silanol
PhMe2SiOH (246 µL, 1.5 mmol) and 0.3 mL o a THF-d8 suspension o Ru⋅SNS40.5
(7.5 µmol) we e in oduced in o a J. Young al ed NMR- ube. The mix u e was hea ed
a 55 ºC o 24 h. As e ealed by 1H NMR analysis, no eac ion occu ed unde hese
condi ions.
Fo ma ion o siloxane om silanol-silane dehyd ogena ion.
In a glo ebox, 0.1 mL o a THF-d8 solu ion con aining dime hylphenylsilane
(115 µL, 0.75 mmol), 0.2 mL o a THF-d8 solu ion con aining dime hylphenylsilanol
(123 µL, 0.75 mmol), and 0.2 mL o a THF-d8 suspension o Ru⋅SNS40.5 (7.5 µmol)
we e in oduced in o a J. Young al ed NMR- ube, which was hea ed a 55 ºC o
24 h. 1H NMR analysis o he c ude eac ion mix u e e ealed he o ma ion o
e ame hyldiphenylsiloxane, (Me2PhSi)2O, as well as he p esence o H2.28
NMR and HRMS da a o ca aly ic eac ion p oduc s
Me2PhSiOH (2a)
The spec oscopic da a o his p oduc ag ee wi h hose p e iously epo ed.47
1H NMR (400 MHz, CD2Cl2): δ 7.59 (m, 2 H, 2 CHPh), 7.38 (m, 3 H, 3 CHPh), 0.36
(s, 6 H, 2 CH3) ppm.
13C{1H} NMR (101 MHz, CD2Cl2): δ 138.3 (CqPh), 133.4, 132.9, 129.3 (2:1:2, CHPh),
-2.1 (CH3) ppm.
(Me2PhSi)2O (3a)
The spec oscopic da a o his p oduc ag ee wi h hose p e iously epo ed.47
1H NMR (400 MHz, CD2Cl2): δ 7.61 (m, 4 H, 4 CHPh), 7.39 (m, 4 H, 4 CHPh), 7.38
(m, 2 H, 2 CHPh), 0.40 (s, 12 H, 4 CH3) ppm.
13C{1H} NMR (101 MHz, CD2Cl2): δ 139.8 (CqPh), 133.1, 129.3, 127.7 (2:1:2, CHPh),
0.62 (CH3) ppm.
47 R. Zeng, M. Felle , Y. Ben-Da id, D. Mils ein, J. Am. Chem. Soc. 2017, 139, 5720-5723.
Ru·SNS nanopa icles
97
HRMS (CI): m/z calcd o C16H22NaOSi2 [(M+Na)+]: 309.1107; ound: 309.1100.
MePh2SiOH (2b)
The spec oscopic da a o his p oduc ag ee wi h hose p e iously epo ed.47
1H NMR (400 MHz, CD2Cl2): δ 7.54 (m, 4 H, 4 CHPh), 7.39 (m, 2 H, 2 CHPh), 7.33
(m, 4 H, 4 CHPh), 0.6 (s, 3 H, CH3) ppm.
13C{1H} NMR (101 MHz, CD2Cl2): δ 137.7 (2 CqPh), 134.0 (4 CHPh), 129.7 (2 CHPh),
127.8 (4 CHPh), -0.74 (CH3) ppm.
HRMS (CI): m/z calcd. o C13H15OSi [(M+H)+]: 215.0892; ound: 215.0887.
[(PhCH2CH2)Me2Si]2O (3c)
1H NMR (400 MHz, CD2Cl2): δ 7.32 (m, 4 H, 4 CHPh), 7.27 (m, 4 H, 4 CHPh), 7.20
(m, 2 H, CHPh) 2.71 ( , 3JHH = 9.1 Hz, 4 H, 2 PhCH2CH2Si), 0.96 ( , 3JHH = 9.1 Hz, 4
H, 2 PhCH2CH2Si), 0.17 (s, 12 H, 4 CH3) ppm.
13C{1H} NMR (101 MHz, CD2Cl2): δ 145.3 (2 CqPh), 128.2, 127.7, 125.4 (2:2:1, 10
CHPh), 29.4 (2 PhCH2CH2Si), 20.4 (2 PhCH2CH2Si), 0.04 (4 CH3) ppm.
HRMS (CI): m/z calcd. o C20H30NaOSi2 [(M+Na)+]: 365.1733; ound: 365.1724.
nP 3SiOH (2d)
The spec oscopic da a o his p oduc ag ee wi h hose p e iously epo ed.48
1H NMR (400 MHz, CD2Cl2): δ 1.42 (m, 6 H, 3 CH2), 1.00 (m, 9 H, 3 CH3), 0.62 (m,
6 H, 3 CH2) ppm.
13C{1H} NMR (101 MHz, CD2Cl2): δ 18.0 (3 CH2), 17.76 (3 CH2), 16.6 (3 CH3) ppm.
HRMS (CI): m/z calcd. o C9H23OSi [(M+H)+]: 175.1518; ound: 175.1509.
(nP 3Si)2O (3d)
1H NMR (400 MHz, CD2Cl2): δ 1.36 (m, 12 H, 6 CH2), 0.96 (m, 18 H, 6 CH3), 0.53
(m, 12 H, 6 CH2) ppm.
13C{1H} NMR (101 MHz, CD2Cl2): δ 18.5 (6 CH2), 18.2 (6 CH2), 16.8 (6 CH3) ppm.
HRMS (CI): m/z calcd. o C18H43OSi2 [(M+H)+]: 331.2852; ound: 331.2841.
48 K. Shimizu, K. Shimu a, N. Imaiida, A. Sa suma, J. Mol. Ca al. A: Chemical 2012, 365, 50-
54.
Chap e III
98
(E O)3SiOH (2 )
The spec oscopic da a o his p oduc ag ee wi h hose p e iously epo ed.49
1H NMR (400 MHz, CD2Cl2): δ 3.82 (q, 3JHH = 7.0 Hz, 6 H, 3 CH2), 1.25 ( , 3JHH =
7.0 Hz, 9 H, 3 CH3) ppm.
13C{1H} NMR (101 MHz, CD2Cl2): δ 59.0 (3 CH2), 18.6 (3 CH3) ppm.
HRMS (CI): m/z calcd. o C6H17O4Si [(M+H)+]: 181.0896; ound: 181.0888.
[(E O)3Si]2O (3 )
The spec oscopic da a o his p oduc ag ee wi h hose p e iously epo ed.50
1H NMR (400 MHz, CD2Cl2): δ 3.82 (q, 3JHH = 7.0 Hz, 12 H, 6 CH2), 1.22 ( , 3JHH =
7.0 Hz, 18 H, 6 CH3) ppm.
13C{1H} NMR (101 MHz, CD2Cl2): δ 59.0 (6 CH2), 17.9 (6 CH3) ppm.
HRMS (CI): m/z calcd. o C12H30NaO7Si2 [(M+Na)+]: 365.1428; ound: 365.1418
49 V. Kazako a, O. B. Go ba se ich, A. M. Muza a o , Russ. Chem. Bull. 2005, 54, 1350-1351.
50 N. Ueda, T. Gunji, Y. Abe, J. Sol-Gel Sci. Technol. 2008, 48, 163-167.
Ru·SNS nanopa icles
99
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25 S. E. Denma k, C. S. Regens, Acc. Chem. Res. 2008, 41, 1486-1499.
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Ru·SNS nanopa icles
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31 R. K. Ramamoo hy, K. Soulan ica, I. Del Rosal, R. A enal, P. Deco se, J-Y.
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44 S. Zhang, C. Wang, Me hods P o oc. 2023, 6, 63-68.
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Chap e III
102
50 N. Ueda, T. Gunji, Y. Abe, J. Sol-Gel Sci. Technol. 2008, 48, 163-167.
Chap e IV:
Fi s ow ansi ion me al nanopa icles
s abilised by NHC ligands as ca alys s o he
me hanolysis o ammonia-bo ane
Chap e IV o his PhD hesis p ima ily ocuses on he syn hesis and cha ac e isa ion
o i on, cobal and nickel nanopa icles using imidazole-2-ylidene ca benes as
s abilising agen s. These colloids ha e demons a ed ac i i y in he me hanolysis o
H3N·BH3, a p ocess ha eleases hyd ogen gas.
Chap e IV
110
ocus on second o hi d ow ansi ion me als. To da e, he e a e ew examples in he
li e a u e desc ibing NHC-s abilised 1s ow ansi ion me al nanopa icles, wi h mos
examples concen a ing on nickel.9 Consequen ly, explo ing he use o ca benes o
s abilise cobal o i on nanopa icles p esen s a p omising esea ch ield.
Among he a ious me als, 2nd and 3 d ow ansi ion me als o en exhibi
highly desi able ca aly ic p ope ies; howe e , hei ela i ely high cos and limi ed
a ailabili y es ic hei la ge-scale use. In con as , 1s ow ansi ion me als o e
ad an ages in e ms o economic easibili y and a o dabili y. They a e gene ally sa e
o human heal h and ha e a lowe en i onmen al impac compa ed o p ecious
me als. A majo ocus in con empo a y ca alysis is he de elopmen o ca alys s based
on ea h abundan elemen s o g een ene gy applica ions, including i on, cobal o
nickel, among o he s.10
Addi ionally, sus ainable ene gy p oduc ion is one o he mos p essing
challenges o he 21s cen u y, d i en by he deple ion o ossil uel ese es and he
ad e se e ec s o clima e change associa ed wi h he con inued use o non- enewable
ene gy sou ces.11 Fossil uels a e esponsible o unp eceden ed le els o a mosphe ic
CO2, signi ican ly con ibu ing o he g eenhouse e ec and he ongoing ise o global
a e age empe a u es.12 Cu en ly, scien i ic consensus in pee - e iewed li e a u e
indica es ha he an h opogenic in luence on global wa ming exceeds 99%.13
The e o e, he e is an u gen need o iden i y new ene gy sou ces o mee he g owing
ene gy demand, which has su ged since he indus ial e olu ion. Among a ious
s udied echnologies, an economy based on hyd ogen as an ene gy ec o , he so-
called hyd ogen economy, is iewed as a leading al e na i e o he p edominan use
o ossil uels.14 Hyd ogen (H2) se es as a iable ene gy s o age me hod, wi h
9 D. Bouzoui a, J. M. Asensio, V. P ei e , A. Palazzolo, P. Lecan e, G. Pie e s, S. Feuillas e,
S. T ica d, B. Chaud e , Nanoscale 2020, 12, 15736-15742.
10 J. I. an de Vlug , Eu . J. Ino g. Chem. 2012, 363-375.
11 N. A ma oli, V. Balzani, Angew. Chem. In . Ed. 2007, 46, 52-66.
12 B. J. an Ruij en, E. De Cian, I. S. Wing, Na . Commun. 2019, 10, 2762.
13 M. Lynas, B. Z. Houl on, S. Pe y, En i on. Res. Le . 2021, 16, 114005.
14 S. S ude , S. S ucki, J. D. Speigh in Hyd ogen as a Fu u e Ene gy Ca ie , Chap e 3, 23-
68, A. Zu el, A. Bo gschul e, L. Schlapbach (Eds-in-Chie ), Wiley-VCH, 2008

111
1s ow ansi ion me al·NHC nanopa icles
po en ial applica ions in bo h s a iona y and mobile se ings. The e o e, i is no
su p ising ha he gene a ion o hyd ogen om enewable sou ces, along wi h i s sa e
and e e sible s o age, a e cu en ly e y ac i e ields o esea ch.15 Addi ionally, he
g a ime ic ene gy densi y o hyd ogen is e y high, 120 MJ/kg ( o compa ison,
gasoline is only 47 MJ/kg) and i s combus ion eac ion p oduces only wa e .16,17 Fo
hese easons, a ansi ion om liquid ossil uel ene gy sou ces o a sus ainable
hyd ogen economy is expec ed o occu wi hin his cen u y.17
Howe e , a hyd ogen-based economy is no inhe en ly g een. Cu en ly, abou
90% o hyd ogen is p oduced h ough he s eam e o ming p ocess (illus a ed in
Scheme 1) o simila me hods ha u ilise a ious o ganic molecules, such as glyce ol
o p opane, esul ing in ca bon dioxide emissions.18,19,20 Hyd ogen p oduced h ough
his p ocess is e e ed o as “g ey hyd ogen”, dis inguishing i om he enewable
“g een hyd ogen”. In ecen yea s he e m “blue hyd ogen” has gained isibili y,
deno ing he in eg a ion o ca bon cap u e echnologies (o CCUS, ac onym o
Ca bon Cap u e, U ilisa ion and S o age) wi h s eam e o ming, he eby con ibu ing
o he educ ion o CO2 emissions.21
Scheme 1. S eam e o ming o me hane.
Al hough no as ex ensi e as o he p ocesses, elec ochemical wa e spli ing
(also called wa e elec olysis) is pa icula ly p omising in e ms o hyd ogen
15 A. Zü el in Ca alysis o Sus ainable Ene gy P oduc ion, Chap e 5, 109-169, P. Ba ba o,
C. Bianchini (Eds-in-Chie ), Wiley-VCH, 2009.
16 M. Ball, M. Weeda, In . J. Hyd ogen Ene gy 2015, 40, 7903-7919.
17 F. Qu eshi, M. Yusu , M. A. Khan, H. Ib ahim, B. C. Ekeoma, H. Kamyab, M. M. Rahman,
A.
K. Nadda, S. Chelliapan, Fuel 2023, 340, 127574.
18 M. Mosinska, M. I. Szynkowska, P. Mie czynski, Ca alys s 2020, 10, 896.
19 M. E. Sad, H. A. Dua e, Ch. Vigna i, C. L. Pad ó, C. R. Apes eguía, In . J. o Hyd ogen
Ene gy 2015, 40, 6097-6106.
20 A. Di Na do, M. Po a apillo, D. Russo, A. Di Benede o, In . J. o Hyd ogen Ene gy 2024,
55, 1143-1160.
21 J. Ince -Val e de, A. Ko ayem, G. Tsa sa onis, T. Mo osuk, Ene gy Con e sion and
Managemen 2023, 291, 117294.
112
Chap e IV
p oduc ion. As Scheme 2 summa ises, his eac ion consis s o an elec oly ic up u e
o a wa e molecule, wi h he subsequen p oduc ion o oxygen (Oxygen E olu ion
Reac ion, OER) and hyd ogen (Hyd ogen E olu ion Reac ion, HER), depending on
he pa icula hal - eac ion. Howe e , his eac ion is no he modynamically
spon aneous unde s anda d s a e condi ions, gi en ha i s change in ee ene gy is
∆G0 = + 237 kJ/mol H2 o , in e ms o po en ial, ∆E0 = -1.23 V. I his ene ge ic
equi emen is sa is ied by sunligh , i is possible o e e he spli ing o wa e as a
pho oelec ochemical p ocess.22 This pho oelec ochemical echnique, also known as
“a i icial pho osyn hesis”, could couple sola ene gy wi h hyd ogen p oduc ion in an
easy, cheap and sus ainable way, eno mously con ibu ing o he adop ion o a g een
hyd ogen economy.23,24,25 Al hough cu en ly he wa e spli ing p ocess con ibu es
4% o global hyd ogen p oduc ion, se e al epo ed cases o di e en expe imen al
se ings achie e his eac ion in a spon aneous way. The e o e, i s ela i e impo ance
is expec ed o g ow in he nea u u e in compa ison o ossil uels.22
Scheme 2. Hal - eac ions o wa e spli ing: Hyd ogen E olu ion Reac ion (HER)
and Oxygen E olu ion Reac ion (OER).
Gi en he physical p ope ies o hyd ogen, pa icula ly i s high lammabili y,
and he necessi y o p oducing hyd ogen abundan ly and cleanly, he de elopmen o
22 J. W. Age , M. R. Shane , K. A. Walczak, I. D. Sha p, S. A do, Ene gy En i on. Sci. 2015,
8, 2811-2824.
23 E. L. Mille , Ene gy En i on. Sci. 2015, 8, 2809-2810.
24 A. Ra eend a, M. Chand an, R. Dhanusu aman, RSC. Ad . 2023, 13, 3843-3876.
25 H. Hou, J. Muñoz, I. J. Gómez, N. Rome o, X. Sala, J. Ga cía-An ón, Ma e . Today Chem.
2024, 37, 102021.
113
1s ow ansi ion me al·NHC nanopa icles
sa e and economical hyd ogen s o age and elease sys ems is essen ial o
implemen ing a la ge-scale hyd ogen-based economy.
T adi ional app oaches o hyd ogen s o age, such as comp essed o lique ied
hyd ogen, equi e ex eme condi ions o p essu e (300-700 ba ) o empe a u e (below
-252 ºC).26 Howe e , some hyd ogen applica ions ely on easy consump ion in uel
cells, which can be challenging wi h exis ing s o age echniques based on p essu ised
and lique ied gas.27 A uel cell is a de ice ha con inuously con e s chemical ene gy
in o elec ici y. While he e a e a ious ypes o uel cells, hyd ogen uel cells a e
cha ac e ised by hei abili y o elec ochemically con e hyd ogen and oxygen in o
elec ical ene gy, p oducing only wa e as a byp oduc . Because hey do no emi CO2
o o he pollu an s, hyd ogen uel cells p esen an a ac i e clean al e na i e o
adi ional in e nal combus ion engines ha use diesel o gasoline.28 Among o he
equi emen s, hyd ogen uel cells need a supply o high pu i y hyd ogen. The e o e,
i is c ucial o de elop sa e and e icien hyd ogen ca ie s capable o eleasing H2
be o e use and allowing ope a ion unde milde condi ions. No ably, he s o age o
hyd ogen in chemical compounds (hyd ogen ca ie s) h ough he e e sible
o ma ion o co alen bonds has ecei ed conside able a en ion.29
In gene al, hyd ogen ca ie s can be ca ego ised in o wo main ypes: hyd ides
o ligh -weigh elemen s (HLEs) and physical so ben s o H2. HLEs a e pa icula ly
in e es ing due o hei high g a ime ic H2 con en s, wi h no able examples including
bo ohyd ides, amide-hyd ides, and ammonia-bo ane along wi h i s de i a i es.30-33
26 D. Clema is, D. Bello i, M. Ri a olo, L. Magis i, A. Ba bucci, Ene gies 2023, 16, 6035.
27 L. Fan, Z. Tu, S. H. Chan, Ene gy Rep. 2021, 7, 8421-8446.
28 O. Z. Sha a , M. F. O han, Renewable Sus ainable Ene gy Re . 2014, 32, 810-853.
29 T. He, P. Pach ule, H. Wu, Q. Xu, P. Chen, Na . Re . Ma e . 2016, 1, 16059.
30 A. Zü el, P. Wenge , S. Ren sch, P. Sudan, Ph. Mau on, Ch. Emmenegge , J. Powe Sou ces
2003, 118, 1-7.
31 P. Chen, Z. Xiong, J. Luo, J. Lin, K. L. Tan, Na u e 2002, 420, 302-304.
32 A. Gu owska, L. Li, Y. Shin, C. M. Wang, X. S. Li, J. C. Linehan, R. S. Smi h, B. D. Kay,
B.
Schmid, W. Shaw, M. Gu owski, T. Au ey, Angew. Chem. In . Ed. 2005, 44, 3578-3582.
33 L. Li, Q. Gu, Z. Tang, X. Chen, Y. Tan, Q. Li, X. Yu, J. Ma e . Chem. A 2013, 1, 12263-
12269.
114
Chap e IV
Ammonia-bo ane (H3N·BH3, AB) is a non- lammable, non- oxic whi e solid
wi h a e y high hyd ogen con en o 19.5 w %. I is soluble in pola sol en s such as
wa e and me hanol and emains s able unde a mosphe ic p essu e and oom
empe a u e. These cha ac e is ics make H3N·BH3 an excellen hyd ogen ca ie .
Fo decades, he syn hesis o ammonia-bo ane has in ol ed he use o sodium
o li hium bo ohyd ide, ammonium sal s and complex isola ion s eps a low
empe a u es (a ound -75 ºC).34,35,36 Howe e , in 2007, Ramachand an e al. epo ed
a simple and apid syn hesis ollowed by an easy pu i ica ion p ocess ha in ol es
only a il a ion s ep (Scheme 3). 37 This syn he ic p ocedu e is cu en ly being u ilised
on a labo a o y scale.
Scheme 3. Syn hesis o ammonia-bo ane.
On he o he hand, hyd ogen s o ed in AB can be eleased h ough a ious
me hods, including he molysis, dehyd ogena ion, hyd olysis o me hanolysis.38,39
Bo h he molysis and dehyd ogena ion sha e a signi ican d awback: o ob ain he
h ee equi . o H2 con ained in he molecule, each successi e s ep gene a es mul iple
seconda y p oduc s ha a e o en poo ly de ined and cha ac e ised. In he case o
he molysis, as simpli ied in Scheme 4, he elease o each subsequen equi . o H2
equi es p og essi ely highe empe a u es. The ini ial s ep, which equi es
empe a u es be ween 90-130 ºC, p oduces polyaminobo anes (H2NBH2)x. The
second s ep, which equi es signi ican ly highe empe a u es, 130-350 ºC, gene a es
polyiminobo anes (also known as bo azines, (HNBH)x) as by-p oduc s. The hi d s ep
34 S. G. Sho e, R. W. Pa y, J. Am. Chem. Soc. 1955, 77, 6084-6085.
35 M. G. Hu, J. M. Van Paasschen, R. A. Geanangel, J. Ino g. Nucl. Chem. 1977, 39, 2147-
2150.
36 E. Maye , Ino g. Chem. 1973, 12, 1954-1955.
37 P. V. Ramachand an, P. D. Gaga e, Ino g. Chem. 2007, 46, 7810-7817.
38 D. Sun, V. Mazumde , O. Me in, S. Sun, ACS Ca al. 2012, 2, 1290-1295.
39 A. Rossin, M. Pe uzzini, Chem. Re . 2016, 116, 8848-8872.
1s ow ansi ion me al·NHC nanopa icles
115
o his he mal decomposi ion equi es empe a u es exceeding 350 ºC, making i
uncommon o obse e he elease o he hi d equi . o H2 in conjunc ion wi h he
subsequen bo on ni ides (NB)x.40,41 I is impo an o no e ha only he dominan
p oduc s a e men ioned he e, as ola ile by-p oduc s a e challenging o cha ac e ise.42
In he case o he ammonia-bo ane dehyd ogena ion p ocess, summa ised in Scheme
5, hyd ogen gas is p oduced along wi h seconda y by-p oduc s such as
polyaminobo anes and polyiminobo anes. Simila ly o he molysis, he elease o he
hi d hyd ogen equi . is pa icula ly di icul and equi es mo e se e e condi ions.41,43
Scheme 4. The molysis o ammonia-bo ane.
On he con a y, he hyd olysis and me hanolysis o AB a e pa icula ly
in iguing due o hei high hyd ogen gene a ion po en ial and he o ma ion o a
well-de ined seconda y p oduc , NH4BO2 in he case o hyd olysis o NH4B(OMe)4
o he me hanolysis case.43
40 A. S aubi z, A. P. M. Robe son, I. Manne s, Chem. Re . 2010, 110, 4079-4124.
41 X. Zhang, L. Kam, T. J. Williams, Dal on T ans. 2016, 45, 7672-7677.
42 P. Wang, Dal on T ans. 2012, 41, 4296-4302.
43 H. Li, Z. Yao, X. Wang, Y. Zhu, Y. Chen, Ene gy Fuels 2022, 36, 11745-11759.

Chap e IV
116
Scheme 5. O e iew o seconda y p oduc s ob ained by dehyd ogena ion o
ammonia-bo ane.
Fu he mo e, he abili y o ca y ou hese eac ions a oom empe a u e along
wi h he op ion o egene a e AB om he seconda y solid p oduc s (NH4B(OMe)4 o
NH4BO2, Scheme 6) a e no able ad an ages.37,41 Me hanolysis is specially p omising
because i o e s a wide ange o applicable empe a u es owing o he lowe eezing
poin o me hanol (-98 ºC) compa ed o ha o wa e (0 ºC).
Scheme 6. Hyd olysis and me hanolysis o ammonia-bo ane.
The i s p eceden o AB me hanolysis was epo ed by Ramachand an e al.
as illus a ed in Scheme 7.37 Thei p o ocol in ol ed he use o a u henium sal ,
RuCl3, o ca alyse he eac ion unde mild empe a u e condi ions (25 ºC) gene a ing
nea ly 3 equi . o hyd ogen wi hin one minu e. The esea ch ocused on he
cha ac e isa ion o a seconda y solid p oduc , ammonium e ame hoxybo a e, which
1s ow ansi ion me al·NHC nanopa icles
117
was isola ed as a c ys alline ma e ial con aining wo me hanol molecules o
c ys allisa ion.
Scheme 7. Fi s epo ed example o ammonia-bo ane me hanolysis.
Since hen, a wide a ie y o ca aly ic sys ems o ammonia-bo ane
me hanolysis has been desc ibed in he li e a u e. These sys ems p ima ily consis o
nanopa icle-based ca alys s, hough he e a e also a ew examples o homogeneous
complexes capable o pe o ming H3N·BH3 me hanolysis.43,44,45 Some ep esen a i e
cases a e discussed in he ollowing pa ag aphs and summa ised in Table 1.46-49
Fo example, Jagi da e al. epo ed a se ies o cobal and nickel based
nanocomposi es, namely Co-Co2B and Ni-Ni3B, syn hesised by educing Co2+ and
Ni2+ sal s, espec i ely.45 They ob ained mos ly agglome a ed samples, al hough a
small numbe o nanopa icles wi h mean sizes be ween 4-8 nm we e also p esen .
These nanocomposi es (Table 1, en ies 1 and 2) we e ound o ca alyse ammonia-
bo ane me hanolysis, exhibi ing TOF o 7.5 and 5.0 min-1 o Co-Co2B and Ni-Ni3B,
espec i ely. Mo eo e , his is no he only example o a nickel nanoca alys capable
o ca alysing AB me hanolysis. La e , Özka e al. desc ibed a se ies o nickel(0)
nanopa icles s abilised by poly inylpy olidone (PVP) wi h an a e age pa icle size
o 3.0 (0.7) nm.46 This sys em p o ed o be ca aly ically ac i e in bo h hyd azine
bo ane and ammonia-bo ane me hanolysis, exhibi ing a TOF alue o 12.1 min-1 in
he la e case (Table 1, en y 3). Ano he no ewo hy example was epo ed by Sun e
44 V. San Nacienceno, M. A. Ga alda, J. M. Ma xain, Z. F eixa, O ganome allics 2020, 39,
1238-1248.
45 S. B. Kalidindi, A. A. Ve neka , B. R. Jagi da , Phys. Chem. Chem. Phys. 2009, 11, 770-775.
46 D. Özha a, N. Z. Kiliçaslan, S. Özka , App. Ca al. B: En i onmen al 2015, 162, 573-582.
47 C. Yu, J. Fu, M. Muzzio, T. Shen, D. Su, J. Zhu, S. Sun, Chem. Ma e . 2017, 29, 1413-1418.
48 P. La a, A. Suá ez, K. Philippo , ChemCa Chem 2019, 11, 766-771.
49 N. Cane , M. Yu de i, A. Bulu , G. S. Kanbe oglu, M. Kaya, M. Zahmaki an, New. J. Chem.
2020, 44, 12435-12439.
Chap e IV
118
al., who desc ibed a bime allic CuNi nanoalloy assembled on g aphene (Table 1, en y
4) which exhibi ed a TOF alue o 49.1 min-1, one o he highes alues epo ed o
non-noble me als.47
In compa ison o he examples p e iously men ioned, ca alys s based on noble
me als gene ally exhibi supe io ca aly ic pe o mance. Fo ins ance, P. La a e al.
syn hesised a se ies o small pla inum nanopa icles (1.5-2.2 nm), s abilised by
e phenylphosphane ligands which we e ound o be highly ac i e in gene a ing H2
om AB. No ably, he sample p epa ed wi h dime hyl-2,6-bis(2’,6’-
di(isop opyl)phenyl)phenylphosphane, e e ed o as L3 in hei wo k, demons a ed
a TOF alue o 284 min-1 (Table 1 en y 5).48 Addi ionally, ega ding a noble me al,
Zahmaki an e al. epo ed a he e ogeneous sys em consis ing o palladium
nanopa icles s abilised by a me al o ganic amewo k; Pd@MIL-101 (MIL-101 =
(C 3F(H2O)2O{O2CC6H4(CO2)}3·nH2O). This ca alys exhibi ed he highes ac i i y
among all he examples desc ibed, wi h a TOF alue o 1080 min-1 (Table 1 en y 6).49
Table 1. Rep esen a i e examples o ca aly ic pe o mance in AB me hanolysis
epo ed in he li e a u e.
En y Ca alys T (ºC)
TOF (min
-1
)
Me al loading
(mol%)
1
Nano Co−Co
2
B
25
7.5
20
2
Nano Ni−Ni
3
B
25
5.0
20
3
PVP-s abilised Ni
25
12.1
0.5
4
Cu
36
Ni
64
/G aphene
25
49.1
7.2
5
P ∙L30.2
30
284
0.19
6
Pd@MIL-101
25
1080
0.037
As p e iously men ioned, while noble-me al ca alys s exhibi excellen
ca aly ic p ope ies, hey a e less a ac i e o cos -e ec i e applica ions compa ed
o mo e a o dable me als. To add ess his, a ious esea ch e o s a e ocused on
de eloping ca alys s based on i s - ow ansi ion me als.
Chap e IV o his PhD Thesis ocuses on he de elopmen o 1s ow ansi ion
me al nanopa icles s abilised by uNHC ligands and he s udy o hei ca aly ic
pe o mance in he me hanolysis o H3N·BH3.
1s ow ansi ion me al·NHC nanopa icles
119
4
4.2 Resul s and Discussion
4.2.1 Syn hesis o IMes and IP NHC ligands
1,3-bis-(2,4,6- ime hylphenyl)imidazol-2-ylidene (IMes) and 1,3-bis-(2,6-
diisop opylphenyl)imidazol-2-ylidene (IP ) ha e been syn hesised ollowing
p e iously epo ed p ocedu es as shown in Scheme 8.50 The condensa ion o glyoxal
wi h he co esponding aniline (2,4,6- ime hylaniline o 2,6-diisop opylaniline)
p oduces a diazabu adiene, which is hen con e ed in o he co esponding NHC·HCl
sal h ough ea men wi h HCl and pa a o maldehyde. Subsequen ly, ea men o
he eac ion mix u e wi h HBF4 acili a es he exchange o he Cl- anion o BF -.
Finally, dep o ona ion o he sal wi h NaH allows o he isola ion o he
co esponding NHC wi h excellen pu i y and high yields (see sec ion 4.3.2 o u he
de ails).
Scheme 8. Syn hesis o IMes and IP ligands.
4.2.2 Syn hesis and cha ac e isa ion o 1s ow ansi ion me al·NHC NPs
The syn hesis o ca bene-s abilised i on, cobal o nickel nanopa icles using
NHCs (N-he e ocyclic ca benes) was conduc ed ollowing he o ganome allic
app oach ou lined in Scheme 9. The co esponding o ganome allic p ecu so ,
{Fe[N(SiMe3)2]2}2, [Co(COE)(COD)], o [Ni(COD)2], whe e COE = 1-cyclooc ene
and COD = 1,5-cyclooc adiene, was decomposed unde 3 ba o H2 in he p esence o
a subs oichiome ic amoun o he app op ia e uNHC ligand (Scheme 9). The eac ion
50 X. Ban eil, S. P. Nolan, Na . P o oc., 2011, 6, 69-77.
Chap e IV
126
in he HRTEM images, illus a ed in Figu e 11, co esponds o he planes o he cc
s uc u e o Ni(0) and Ni2O4 species, consis en wi h li e a u e epo s.46 In addi ion o
HRTEM cha ac e isa ion, analysis ia STEM-EDX, including in ensi y maps (Figu e
12), con i med he nickel composi ion o he nanopa icles. While he p esence o a
peak o ni ogen may be a ibu ed o pa ial decomposi ion o he ca bene ligand, a
peak co esponding o oxygen was also obse ed, likely due o he p esence o Ni2O4.
Figu e 11. HRTEM image (le ) and Fas Fou ie T ans o m o spa ial equencies
( igh ) co esponding o Ni·IMes0.2.
400
360
320
280
240
200
160
120
80
40
0
001
0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 10.00
keV
Figu e 12. STEM-EDX analysis (le ) and in ensi y map ( igh ) o Ni·IMes0.2.
On he o he hand, HRTEM o Ni·IP 0.2 NPs e ealed signi ican
disc epancies compa ed o he esul s ob ained o Ni·IMes0.2. Figu e 13 p esen s a
HRTEM image o Ni·IP 0.2 and i s co esponding FFT, whe e he in e plana dis ances
Coun s
CKa
NKa
OKa
FKa
NiLl NiLa CuLa
SiKa
NiKa
CuKa
NiKb
CuKb

1s ow ansi ion me al·NHC nanopa icles
127
ound co espond o he hcp s uc u e o Ni3O6, while no dis ances associa ed wi h cc
s uc u e o Ni(0) we e de ec ed.
Figu e 13. HRTEM image (le ) and Fas Fou ie T ans o m o spa ial equencies
( igh ) co esponding o Ni·IP 0.2.
The composi ion and chemical s a e o he nanopa icle su ace was analysed
using XPS by D . Flo encia Va ie Laga igue a he “Ins i u o de Ciencia de
Ma e iales de Se illa” (ICMS). In all cases, he ob ained spec a we e qui e complex,
ea u ing peaks wi h a ious mul iple s and a signi ican con ibu ion om oxidised
species, despi e ca e ul handling o he samples.
The high esolu ion XPS spec um o 2p egion o Fe·IMes0.5 dis inguishes
wo mul iple s cen ed a 709.4 eV and 723.3 eV, co esponding o he Fe 2p3/2 and Fe
2p1/2 egion, espec i ely. The Fe 2p3/2 signal can be i ed in o h ee main con ibu o s:
Fe(0) a 706.3 eV (Figu e 14a, op, blue line), and oxidised Fe species: FeO (Figu e
14a, op, g een line) and Fe2O3 (Figu e 14a, op, b own line).53 Figu e 14b p esen s
he spec um o he N 1s egion o Fe·IMes0.5, showing a peak a 399.9 eV ha
con i ms he p esence o he ligand in he sample. This binding ene gy co esponds o
a displacemen o 1.1 eV ela i e o ee IMes (401 eV). This echnique enables he
es ima ion o me al oxida ion a he su ace o he pa icles. The p opo ion o me allic
53 M. C. Biesinge , B. P. Payne, A. P. G os eno , L. W.M. Lau, A. R. Ge son, R. S .C. Sma ,
Appl. Su . Sci. 2011, 257, 2717-2730.
Chap e IV
128
Fe(0) accoun ed o only 4% o he o al, and inc eased o 15% a e su ace cleaning
by mild condi ion spu e ing wi h ionised a gon (Figu e 14a, bo om).
Figu e 14. a) XPS spec a o he Fe 2p3/2 egion o Fe·IMes0.5, p io o (bo om) and
a e ( op) mild condi ions spu e ing wi h ionised a gon. b) XPS spec a o he N 1s
egion o he esh Fe·IMes0.5 (bo om) and he ee IMes ligand ( op).
Equi alen esul s we e ob ained o Fe·IP 0.5 sample, wi h he co esponding
spec a ep esen ed in Figu e 15. In his case, he con ibu ion o i on in he ze o-
oxida ion s a e was 3%, which inc eased o 23% a e he emo al o he oxidised
ex e nal laye .
Figu e 15. a) XPS spec a o he Fe 2p3/2 egion o Fe·IP 0.5, p io o (bo om) and
a e ( op) mild condi ions spu e ing wi h ionised a gon. b) XPS spec a o he N 1s
egion o he esh Fe·IP 0.5 (bo om) and he ee IP ligand ( op).
1s ow ansi ion me al·NHC nanopa icles
129
Fo Co·IMes0.2, he co esponding XPS spec um displays wo mul iple s
cen ed a 782.6 and 799.7 eV o binding ene gy (BE), a ibu ed o spin o bi spli ing
o Co 2p3/2 and Co 2p1/2, espec i ely. The Co 2p3/2 signal (Figu e 16) could be
decon olu ed in o h ee main componen s: me allic cobal a 778.2 eV BE (blue cu e)
and he oxidised species (Co+2 y Co+3, g een and b own line, espec i ely).53,54 The
dep h o he oxida ion laye can be assessed by a ying he measu emen angle ela i e
o he analyse . A a 0º angle, he me al con ibu ion in a omic concen a ion (% A ) is
20% (Figu e 16, bo om, blue line), while a 45º, he me al con ibu ion dec eases o
8% (Figu e 16, op, blue line) due o he hinning o he measu ed laye as he angle
inc eases. This indica es ha he oxide is con ined o he su ace laye s o he sample.
792 788 784 780 776
BE (eV)
Figu e 16. XPS spec a o he Co 2p3/2 egion o Co·IMes0.2 egis e ed a 0º
(bo om) and 45º ( op) ake o angles.
The p opo ion o me allic Co(0) inc eases om 20% o 40% a e he
oxidised ma e ial laye was emo ed by ionised a gon spu e ing unde mild
condi ions (Figu e 17a, blue line). I can be assumed ha he condi ions du ing A
spu e ing a e compa able o hose in suspension unde an ine a mosphe e,
54 T. Ma hew, S. Shylesh, B. M. De assy, M. Vijaya aj, C. V.V. Sa yana ayana, B. S. Rao, C.
S. Gopina h, App. Ca al. A 2004, 273, 34-45.
A bi a y Uni s
Chap e IV
130
sugges ing ha cobal p esen ed in ca aly ic nanopa icles is likely in he ze o
oxida ion s a e. This hypo hesis is suppo ed by he posi ion o he Co 2p3/2 peaks o
he educed me al a 778.2 eV, a cha ac e is ic alue o nanoma e ials wi h sizes
a ound 3 nm, which is consis en wi h he mean nanopa icle size ound o
Co·IMes0.2, 2.2 (0.4) nm.55
Figu e 17. a) XPS spec a o he Co 2p3/2 egion o Co·IMes0.2, p io o (bo om)
and a e ( op) mild condi ions spu e ing wi h ionised a gon. b) XPS spec a o he
N 1s egion o he esh Co·IMes0.2 (bo om), he A spu e ed sample (middle) and
he ee IMes ligand ( op).
XPS spec oscopy also con i med he p esence o IMes ligand on he
nanopa icle su ace (Figu e 17b). Fo he ee IMes ligand, he N 1s egion shows a
sha p signal (3.1 eV) cen ed a 401.0 eV (Figu e 17b, op), while his signal is sligh ly
b oade (3.4 eV) and shi ed (399.7 eV) o bo h Co·IMes0.2 samples (Figu e 17b,
55 M. R. Na ouz, C.-H. Li, A. Nazemi, C. M. C udden, Langmui 2017, 33 14211-14219.
1s ow ansi ion me al·NHC nanopa icles
131
bo om- esh sample and middle-spu e ed sample).56-60 This binding ene gy
co esponds o a displacemen o 1.3 eV ela i e o ee IMes, simila o ha obse ed
o Fe·IMes0.5 nanopa icles (Figu e 14b, 1.1 eV).
Co·IP 0.2 nanopa icles exhibi ed simila beha iou o hei IMes-s abilised
coun e pa s, wi h he co esponding spec a shown in Figu e 18. A e cleaning he
su ace by ion A + spu e ing, he amoun o Co in he ze o-oxida ion s a e inc eased
om 19 o 42 %.
Figu e 18. a) XPS spec a o he Co 2p3/2 egion o Co·IP 0.2, p io o (bo om) and
a e ( op) mild condi ions spu e ing wi h ionised a gon. b) XPS spec a o he N 1s
egion o he esh Co·IP 0.2 (bo om) and he ee IP ligand ( op).
56 P. Molinillo, M. Puyo, F. Va ie , B. Lac oix, N. Rendón, P. La a, A. Suá ez, Nanoscale 2023,
15, 14488-14495.
57 L.M. Ma ínez-P ie o, I. Cano, A. Má quez, E. A. Baque o, S. T ica d, L. Cusina o, I. del
Rosal, R. Po eau, Y. Coppel, K. Philippo , B. Chaud e , J. Cámpo a, P. W. N. M. an Leeuwen,
Chem. Sci. 2017, 8, 2931-2941.
58 N. B idonneau, L. Hippoly e, D. Me cie , D. Po ehaul , M. Desage-El Mu , P. Ma cus, L.
Fens e bank, C. Chanéac, F. Ribo , Dal on T ans. 2018, 47, 6850-6859.
59 L. M. Ma ínez-P ie o, L. Rake s, A. M. López-Vinasco, I. Cano, Y. Coppel, K. Philippo , F.
Glo ius, B. Chaud e , P. W. N. M. an Leeuwen, Chem. Eu . J. 2017, 23, 12779-12786.
60 A. Rühling, K. Schaepe, L. Rake s, B. Vonhö en, P. Tegede , B. J. Ra oo, F. Glo ius, Angew.
Chem. In . Ed. 2016, 55, 2016, 5856-5860.

Chap e IV
132
The XPS spec um o Ni·IMes0.2 nanopa icles shows he Ni 2p egion,
dis inguishing wo main g oups o signals cen ed a binding ene gies o 852.9 and
869.9 eV, associa ed o he Ni 2p3/2 and Ni 2p1/2 pho oemission peaks, espec i ely.
The Ni 2p3/2 signal can be decon olu ed in o h ee main con ibu o s: Ni(0) a 852.5
eV (Figu e 14a, blue line),53,61,62,63 and oxidised Ni species: NiO2 (Figu e 14a, g een
line) and Ni(OH)2 (Figu e 14a, b own line). This Ni(0) peak signi ican ly inc eased
a e a gon spu e ing (Figu e 19a, op, blue line) compa ed o he spec um o he
esh sample (Figu e 19a, bo om, blue line), indica ing ha he con ibu ion o Ni(0)
ises om 11% in he esh sample o 75% in he spu e ed sample. To con i m ligand
coo dina ion on he su ace o Ni·IMes0.2, a high- esolu ion spec um o he N 1s
egion was eco ded, as illus a ed in Figu e 19b. The posi ion o he peak
co esponding o Ni·IMes0.2 a 400.9 eV (Figu e 19b, bo om) is e y simila o ha
o he ee IMes ligand, 401.0 eV (Figu e 19b, op).
Figu e 19. a) XPS spec a o he Ni 2p3/2 egion o Ni·IMes0.2, p io o (bo om) and
a e ( op) mild condi ions spu e ing wi h ionised a gon. b) XPS spec a o he N 1s
egion o he esh Ni·IMes0.2 (bo om) and he ee IMes ligand ( op).
61 A. P. G os eno , M. C. Biesinge , R. S .C. Sma , N. S. McIn y e, Su . Sci. 2006, 600, 1771-
1779.
62 M. C. Biesinge , B. P. Payne, L. W. M. Lau, A. Ge son, R. S .C. Sma , Su . In e ace Anal.
2009, 41, 324-332.
63 A. M. López-Vinasco, L. M. Ma ínez-P ie o, J. A. Asensio, P. Lecan e, B. Chaud e , J.
Cámpo a, P. W. N. M. an Leeuwen, Ca al. Sci. Tech. 2020, 10, 342.
1s ow ansi ion me al·NHC nanopa icles
133
A simila beha iou was obse ed o Ni·IP 0.2, wi h he co esponding
spec a shown in Figu e 20. A e su ace cleaning by A + ion spu e ing, he
p opo ion o Ni in he ze o-oxida ion s a e inc eases om 13% o 65%.
Figu e 20. a) XPS spec a o he Ni 2p3/2 egion o Ni·IP 0.2, p io o (bo om) and
a e ( op) mild condi ions spu e ing wi h ionised a gon. b) XPS spec a o he N 1s
egion o he esh Ni·IP 0.2 (bo om) and ee IP ligand ( op).
The ela i e in ensi ies o he co esponding pho oemission signals enabled
he quan i ica ion o Fe, Co, Ni, and N a oms on he su aces o he nanopa icles.
Table 3 p esen s he a omic concen a ions o N and he me als (Fe, Co, and Ni), along
wi h he M/N a io. As expec ed, he su ace co e age deg ee o Fe nanopa icles is
highe han ha o Co and Ni NPs, due o he la ge quan i y o ligand employed in
he Fe NPs syn hesis (0.5 equi . s. 0.2 equi .).
Table 3. Quan i a i e analysis o he su ace composi ion o 1s ow ansi ion
me al·NHC nanopa icles (pe cen age in a omic concen a ion, %A ).
Colloid
M (% A )
N (% A )
M/N
Fe·IMes0.5
32
68
0.5
Fe·IP 0.5
34
66
0.5
Co·IMes0.2
48
52
0.9
Co·IP 0.2
35
65
0.5
Ni·IMes0.2
71
29
2.4
Ni·IP 0.2
46
54
0.9
Chap e IV
134
I is also wo h men ioning ha , al hough he e was no comple e o e lap
be ween he species de ec ed by XPS and HRTEM analysis, bo h echniques ha e
con i med he p esence o Fe(0), Co(0) and Ni(0) in each case, along wi h a clea
con ibu ion om a ious oxidised species. This obse a ion unde sco es he
signi ican sensi i i y o hese h ee me als o ai -exposu e.
The pe cen age o su ace a oms was calcula ed acco ding o he magic
numbe ule,64,65 as in p e ious cases, conside ing cc s uc u e (Table 4) o Fe and
Ni, and hcp s uc u e o Co samples. The es ima ed pe cen ages o su ace a oms o
each nanopa icle a e p esen ed in Table 5.
Table 4. Building o closed-shell clus e s by applying he magic numbe ule o
me als wi h a cc s uc u e.
Nºumbe o shell (n)
0
1
2
3
4
5
Numbe o a oms in shell
1
12
42
92
162
252
Su ace a oms (%)
--
92
76
63
52
45
Numbe o shell (n)
6
7
8
9
10
11
Numbe o a oms in shell
362
492
642
812
1002
1212
Su ace a oms (%)
39
35
31
28
26
24
Table 5. Pe cen age o su ace a oms calcula ed o 1s ow ansi ion me al·NHC
nanopa icles by applying he magic numbe ule.
Colloid
Numbe o a oms
Su ace a oms (%)
Fe·IMes0.5
541
45
Fe·IP 0.5
975
39
Co·IMes0.2
507
52
Co·IP 0.2
659
45
Ni·IMes0.2
1424
35
Ni·IP 0.2
3060
28
64 J. Wang, C. F. Mbah, T. P yzbilla, B. A. Zubi i, E. Spiecke , M. Engel, N. Vogel, Na .
Commun. 2018, 9, 5259.
65 A. F. Schmid , V. V. Smi no , Top. Ca al. 2005, 32, 71-75.
1s ow ansi ion me al·NHC nanopa icles
135
4.2.3 Me hanolysis o AB ca alysed by 1s ow ansi ion me al·NHC NPs
Ammonia-bo ane (H3N·BH3, AB) has gained a en ion as a H2 s o age
molecule in ecen yea s.37,40,66 H3N·BH3 exhibi s se e al ad an ageous p ope ies: i
is a non- lammable, non- oxic, and s able whi e solid (boiling poin 104 ºC) wi h a
e y high hyd ogen con en (19.6 %w ). Unlike me hods such as he mal
decomposi ion o dehyd ogena ion, which ha e limi ed capaci y o ully elease he
maximum a ailable H2, me hanolysis o ammonia-bo ane unde mild condi ions can
yield 3 equi . o H2.48,67 Fu he mo e, as shown in Scheme 10, ammonium
e ame hoxybo a e (NH4B(OMe)4) is he only seconda y p oduc o med du ing his
p ocess. This solid p oduc can be easily econ e ed o H3N·BH3 by ea men wi h
NH4Cl and a s ong educ o like LiAlH4. Addi ionally, he use o nanopa icles o
ca alyse his eac ion is well documen ed in he li e a u e, as p e iously men ioned in
he in oduc ion o his chap e .43
Scheme 10. Me hanolysis o ammonia-bo ane.
The ca aly ic ac i i y o NHC s abilised i s ow ansi ion me al
nanopa icles was e alua ed o H2 gene a ion om me hanol solu ions o H3N·BH3.
This eac ion was pe o med in a closed Fishe -Po e eac o equipped wi h a p essu e
de ec o connec ed o a compu e and he ca aly ic pe o mance was moni o ed by
measu ing he inc ease in gas p essu e. Once no u he changes in p essu e we e
obse ed, he quan i a i e o ma ion o NH4B(OMe)4 was con i med by 11B NMR
spec oscopy analysis, which shows he p esence o only a single a δ 6.9 ppm.
All eac ions we e conduc ed wi h a ca alys loading o 0.34 mol% (S/C =
300) and an ammonia-bo ane concen a ion o 1.25 M in MeOH, wi h he empe a u e
main ained a 30 ºC. Resul s ob ained in such condi ions a e summa ised in Table 6.
66 S. Özka , In . J. Hyd ogen Ene gy 2020, 45, 7881-7891.
67 I. O ega-Lepe, A. Rossin, P. Sánchez, L. L. San os, N. Rendón, E. Ál a ez, J. López-
Se ano, A. Suá ez, Ino g. Chem. 2021, 60, 18490-18502.