Reduction of carbon dioxide and organic carbonyls by hydrosilanes catalysed by the perrhenate anion

Abstract

The simple perrhenate salt [N(hexyl)₄][(ReO₄)] acts as a catalyst for the reduction of organic carbonyls and carbon dioxide by primary and secondary hydrosilanes. In the case of CO₂, this results in the formation of methanol equivalents via silylformate and silylacetal intermediates. Furthermore, the addition of alkylamines to the reaction mixture favours catalytic amine N-methylation over methanol production under certain conditions. DFT analysis of the mechanism of CO₂ reduction shows that the perrhenate anion activates the silylhydride forming a hypervalent silicate transition state such that the CO₂ can directly cleave a Si–H bond.