Effects of silylene ligands on the performance of carbonyl hydrosilylation catalyzed by cobalt phosphine complexes

Abstract

In order to study the effects of silylene ligands in phosphine cobalt complex on the catalytic activity in carbonyl hydrosilylation, readily available model catalyst are required. In this contribution, a...

Co‐Catalyzed Hydrosilylation of Ketones under Base‐Free Conditions: A Convenient Route to Silyl Ethers or Secondary Alcohols

“…However, based on reported theoretical calculations, the insertion of the C=O motif into the M−H bond seems to be in favor of the insertion between the M−Si bond. Finally, the active specie regenerates due to the reductive elimination of the desired product [53,68] . An alternative proposal, which assumes that alkoxyl cobalt complex undergoes transmetalation with Ph 2 SiH 2 , is also presented [69] .…”

“…Based on our mechanistic study and previous literature, we proposed a plausible activation step and catalytic cycle for the hydrosilylation of ketones mediated by PNP-Co pincer complexes (Scheme 6). [36,37,53,55,56,61] Considering the above, it seems reasonable to assume the Co I /Co III pathway involves (PNP)Co I H as an active catalyst. Such [CoÀ H] specie forms after adding diphenylsilane to (PNP)Co II Cl 2 with the simultaneous release of H 2 and the corresponding chlorosilane.…”

“…Finally, the active specie regenerates due to the reductive elimination of the desired product. [53,68] An alternative proposal, which assumes that alkoxyl cobalt complex undergoes transmetalation with Ph 2 SiH 2 , is also presented. [69] As the result, corresponding silyl ether is formed and the complex (PNP)Co III (SiHPh 2 )H 2 is regenerated.…”

“…[52] More recently, Li group studied the effects of silylene ligands on the catalytic activity of carbonyl hydrosilylation catalyzed by cobalt phosphine complexes. [53] Furthermore, an asymmetric hydrosilylation of α-oxygenated ketones was developed under the catalysis of Co(OAc) 2 in combination with a chiral phosphine-amido-oxazoline by Xia and co-workers. [54] Among the employment of various ligands, pincer systems have aroused great interest due to the additional stability brought by the chelation effect, which contributed to their widespread use in valuable catalytic processes.…”

“…al [52] . More recently, Li group studied the effects of silylene ligands on the catalytic activity of carbonyl hydrosilylation catalyzed by cobalt phosphine complexes [53] . Furthermore, an asymmetric hydrosilylation of α ‐oxygenated ketones was developed under the catalysis of Co(OAc) 2 in combination with a chiral phosphine‐amido‐oxazoline by Xia and co‐workers [54] .…”