Phosphazenes: efficient organocatalysts for the catalytic hydrosilylation of carbon dioxide

Abstract

Phosphazene superbases are efficient organocatalysts for the metal-free catalytic hydrosilylation of carbon dioxide. They react with CO₂ to form the respective phosphine oxides, but in the presence of hydrosilanes, CO₂ can be selectively reduced to silyl formates, which can in turn be reduced to methoxysilanes by addition of an extra loading of silanes. Activities reach a TOF of 32 h⁻¹ with a TON of 759. It is also shown that unexpectedly, N,N-dimethylformamide can reduce CO₂ to a mixture of silyl formates, acetals and methoxides in the absence of any catalyst.