Analysis of an unprecedented mechanism for the catalytic hydrosilylation of carbonyl compounds |
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Authors: | Nolin Kristine A Krumper Jennifer R Pluth Michael D Bergman Robert G Toste F Dean |
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Institution: | Department of Chemistry, University of California, Berkeley, California 94720, USA. |
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Abstract: | This work details an in-depth evaluation of an unprecedented mechanism for the hydrosilylation of carbonyl compounds catalyzed by (PPh3)2Re(O)2I. The proposed mechanism involves addition of a silane Si-H bond across one of the rhenium-oxo bonds to form siloxyrhenium hydride intermediate 2 that reacts with a carbonyl substrate to generate siloxyrhenium alkoxide 4, which, in turn, affords the silyl ether product. Compelling evidence for the operation of this pathway includes the following: (a) isolation and structural characterization by X-ray diffraction of siloxyrhenium hydride intermediate 2, (b) demonstration of the catalytic competence of intermediate 2 in the hydrosilylation reaction, (c) 1H and 31P{1H} NMR and ESI-MS evidence for single-turnover conversion of 2 into 1, (d) observation of intermediate 2 in the working catalyst system, and (e) kinetic analysis of the catalytic hydrosilylation of carbonyl compounds by 1. |
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