Carbon Dioxide Reduction to Silyl-Protected Methanol Catalyzed by an Oxorhenium Pincer PNN Complex

Reaction of the rhenium pincer PNN complex [(PNN)Re(O)2][OTf] (2) with Me2PhSiH results in addition of Si–H across the Re═O bond and a complex capable of reducing CO2 under mild conditions (ambient temperature and 100 psig) to silyl formate in 95% yield. Reaction of 2 with PhSiH3 yields a more reactive complex that catalytically reduces silyl formate to silyl formal (85% yield) and over longer times to silyl methanol (53% yield) with extrusion of siloxane. This system represents the unusual case of a high-valent metal oxo complex capable of reducing CO2 in a two-step, one-pot reaction to methanol.