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

Danny S Morris,Mirza Cokoja,Fritz E Kühn,Julian T C Wennmacher,Markus Drees,Catherine Weetman,Jason B Love

doi:10.1039/c7cy00772h

Abstract

A simple quaternary ammonium perrhenate salt catalyses the hydrosilylation of aldehydes, ketones, and carbon dioxide, and the methylation of amines using carbon dioxide. DFT calculations show that a perrhenate hypervalent silicate interacts directly with CO2.

Highlights

It was shown previously that the pyridinium perrhenate salt [4,6-But2C5H2NH-2-CH{(CO)NHIJC6H13)}2]ijReO4] 1 acts as a catalyst for the epoxidation of alkenes by hydrogen peroxide under biphasic conditions.66 Important to this chemistry is the formation of a lipophilic ion pair in which electrostatic and hydrogen-bonding interactions are enhanced in the hydrophobic phase
Given the efficacy of this new catalyst system and the use of high oxidation state rhenium oxo complexes in reduction catalysis, it is shown here that perrhenate can act as a catalyst for the reduction of carbon dioxide to methanol equivalents by hydrosilanes, that the methylation of alkylamines using CO2 as the C1 source occurs under similar catalytic conditions, and that this method can be used to reduce aldehydes and ketones to silylalcohols
We have shown that the simple, lipophilic perrhenate salt [NIJhexyl)4]ijReO4] 2 acts as a catalyst for the reduction of CO2 by hydrosilanes

Summary

Introduction

It was shown previously that the pyridinium perrhenate salt [4,6-But2C5H2NH-2-CH{(CO)NHIJC6H13)}2]ijReO4] 1 acts as a catalyst for the epoxidation of alkenes by hydrogen peroxide under biphasic conditions.66 Important to this chemistry is the formation of a lipophilic ion pair in which electrostatic and hydrogen-bonding interactions are enhanced in the hydrophobic phase. CO2 and at 80 °C, complete consumption of the hydrosilane is observed in the 1H NMR spectrum after 12 h (Fig. S4†) along with the formation of silyformate (3), bisIJsilyl)acetal (4) and silylated methanol (5) products (Table 1, entry 1 and Scheme 1).

Results

Conclusion