RSC Advances
Journal Name
DOI: 10.1039/C4RA09881A
ARTICLE
to unfavored βꢀZ isomer formation, while limiting the By this work, we presented a novel nanocatalysts design based
formation of the ꢀisomer. Neutral homogeneous Rh catalysts on transition metal nanocrystals stabilized by Onium Salts. The
are known to lead to
α
2
4
Z
ꢀvinylsilanes. In our case nonetheless, preparation approach, scCO assisted synthesis, not only afford
2
depending on the Onium Salt, Rh NCs afforded predominantly direct powdered, readyꢀtoꢀuse, air/moisture stable nanocatalyst,
either the βꢀZ or βꢀE isomer and a small amount of α isomer but also highly active hydrosilylation catalyst free from any
(
Table 5, entries 5ꢀ6). Rh@TBAB afforded better yields and undesired organics. Pt@TBAB allowed us to perform efficient
selectivity (for βꢀZ isomer, Table 5, entry 5). In contrast by selective hydrosilylation of phenylacetylene using only 10
using a long chain Onium Salt (Table 3, entry 3 and Table 5, ppm of NC, to date one of the most efficient heterogeneous
entry 6) increased significantly styrene proportion, formed by nanocatalyst. With particular focus on nanocatalysts
hydrodesilylation. One can notice that Rh@CTANTf led to βꢀ morphology and surface properties, to better understand NCs
βꢀE
a
2
E
isomer predominantly albeit in poor yield (Table 5, entry 6). catalytic behaviour, we have presented the implications of some
Unfortunately among all Ru@OS prepared (Table 3, entry 4 experimental parameters on nanocatalysts efficiency. By using
and Table 5, entries 7ꢀ8), only Ru@CTAB seems to be efficient advanced hybrid organicꢀinorganic NCs we successfully made
in the selected hydrosilylation reaction, allowing the formation a step toward hydrosilylation stereoselectivity modulation by: i)
of 68% of βꢀZ isomer and only traces of α (Table 3, entry 4). varying the metal but preserving the same Onium Salt
Moving to a triflimide counter anion annihilates the reaction stabilizer; ii) varying the metal NCs morphology and surface
whereas using TBAB led to a lower conversion albeit in an properties by changing either the stabilizer structure (different
excellent 86% of βꢀZ selectivity (Table 5, entry 7). More anion or cation) or NCs synthesis temperature and iii) varying
surprising was the way Onium Salt affects the selectivity for Ir NCs concentration with direct effect on nanocatalysts
NCs. Indeed, even if Ir@TBAB was the most active NCs, it selectivity. It is worth noticing that this approach led to the first
also led to the lowest selectivity. For example, the Ir NCs examples of selective βꢀZ hydrosilylation catalyzed by
stabilization with CTANTf led to a mixture of the 3 isomers in Ruthenium nanocatalyst.
2
a 1/4/1 ratio (Table 5, entry 4), instead of 1/2/2 with TBAB With further optimization on nanocatalysts surface properties,
(
Table 5, entry 3).
for example using additional ligands, lower reaction yields
obtained for some M@OS systems, can be overcome.
Table 6. Nanocatalysts loading: Pt@TBAB in
phenylacetylene hydrosilylation.
Acknowledgements
Entr
y
Pt@TBA
B ppm
Product distribution (%)
Yiel
d
(%)
The authors want to acknowledge the financial support to the
Aquitaine Region and the ANRꢀ12ꢀCDIIꢀ010ꢀNANOCAUSYS.
b
1
α
4
β−
E
β−
0
Z
4
5
1
2
3
4
10
85
0
5
0
0
0
0
6
3
11
Notes and references
100
26
23
5
71
0
100
100
100
a CNRS, Université de Bordeaux, ICMCB, UPR 9048, Fꢀ33600 Pessac,
France. Dr Cyril Aymonier, ICMCBꢀCNRS, 87 avenue du Dr Albert
Schweitzer, 33608 Pessac Cedex, France. Email : aymonier@icmcbꢀ
bordeaux.cnrs.fr
1,000
10,000
0
67
60
1
9
0
3
32
b CNRS, Université de Bordeaux, ISM, UMR 5255, Fꢀ33405 Talence,
France. Dr Mathieu Pucheault, ISM, 351 cours de la libération 33405
Talence Cedex, France. Email: m.pucheault@ism.uꢀbordeaux1.fr
Alkyne (1 equiv.), silane (1 equiv.), 85°C, 23h were used in
all reactions.
Nanocatalyst concentration
References
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a
,
formed (Table 6). While decreasing the amount of NCs to 100
Hydrosilylation, B. Marciniec, Ed. Springer Netherlands: 2009; Vol.
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1, pp 53ꢀ86.
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, but can 5. R. Jimenez, J. M. MartinezꢀRosales and J. Cervantes, Can. J. Chem.,
3
,
β
ꢀ
Eꢀ
3
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,
8
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