Developing a Highly Active Catalytic System Based on Cobalt Nanoparticles for Terminal and Internal Alkene Hydrosilylation

Abstract

This work describes the development of easy to prepare cobalt nanoparticles (NPs) in solution as promising alternative catalysts for alkene hydrosilylation with the industrially relevant tertiary silane MD H M (1,1,1,3,5,5,5-heptamethyltrisiloxane). The Co NPs demonstrated high activity when used at 30 °C for 3.5-7 h in toluene, with catalyst loadings 0.05-0.2 mol%, without additives. Under these mild conditions, a set of terminal alkenes were found to react with MD H M, yielding exclusively the anti-Markovnikov product in up to 99% yields. Additionally, we demonstrated the possibility of using UV irradiation to further activate these cobalt NPs in order to enhance their catalytic performances, but also to promote tandem isomerization-hydrosilylation reactions using internal alkenes, among them unsaturated fatty ester (methyl oleate), to produce linear products in up to quantitative yields.

Steric Effects in the Catalytic Tandem Isomerization‐Hydrosilylation Reaction

“…This limitation could be solved by a catalyst capable of tandem isomerization-hydrosilylation of an internal alkene in which the previous isomerization from internal to terminal olefins and subsequent α-olefin hydrosilylation is promoted by the same metal complex. Examples of efficient tandem isomerizationhydrosilylation of internal alkenes catalysed by transition metals such as cobalt, [23][24][25] nickel, [26,27] iron, [28] rhodium [29] or ruthenium, [29] or even metal nanoparticles [30,31] have recently been reported. In most of these cases, large metal loadings or dual catalyst systems were necessary to achieve good results.…”

Ni(ii) and Co(ii) bis(acetylacetonato) complexes for alkene/vinylsilane silylation and silicone crosslinking

“…43,44 It could also be the result of Cobased nanoparticles/colloids (Co(0)/Co(I) reduced species) formed in the case of Co(acac) 2 that would induce a different catalytic pathway. 11,12,38,40,41 On the contrary, Ni precatalysts still promote the DS pathway, with identifiable characteristic olefinic protons (Fig. 5a) and carbons (Fig.…”

“…Co catalysis seems more difficult to rationalize, all systems are paramagnetic no matter the geometry and the darkening of the solution (see ESI, † section 9miscellaneous) could suggest reduction to Co(0) or Co(I) species, as previously proposed. [10][11][12]40,41 In the second part of our study, we monitored the activity of these catalysts for the crosslinking of Si-H and Si-vinyl functionalized silicone oils. Harnessing alkene (hydro)silylation to cure silicone formulations is the cornerstone of silicone materials' manufacturing: multiple applications heavily rely on this reaction.…”

“…Nickel, cobalt and iron catalysts have already been reported and reviewed as relatively active and selective for alkene hydrosilylation (HS) and dehydrogenative silylation (DS). [6][7][8][9][10][11][12][13] Two types of systems have been reported in the literature: low-oxidation state and high-oxidation state complexes. Among low oxidation state catalysts, Chirik's bis(imino) pyridine iron(0) 14 and cobalt(I) 15 are seminal examples, which are very active under strict inert conditions.…”

Highly active cobalt complex catalysts used for alkene hydrosilylation

“…In addition, there are some studies on hydrosilylation reactions catalyzed by cobalt salts. [ 18–30 ]…”