Hydrosilylative reduction of carbon dioxide by a homoleptic lanthanum aryloxide catalyst with high activity and selectivity

Abstract

An efficient tandem hydrosilylation of CO₂, which uses a combination of a simple, homoleptic lanthanum aryloxide and B(C₆F₅)₃, was performed. Use of a less sterically hindered silane led to an exclusive reduction of CO₂ to CH₄, with a turnover frequency of up to 6000 h⁻¹ at room temperature. The catalytic system is robust, and 19 400 turnovers could be achieved with 0.005 mol% loading of lanthanum. The reaction outcome depended highly on the nature of the silane reductant used. Selective production of the formaldehyde equivalent, i.e., bis(silyl)acetal, without over-reduction, was observed when a sterically bulky silane was used. The reaction mechanism was elucidated by stoichiometric reactions and DFT calculations.