Catalytic CO 2 Hydrosilylation with [Mn(CO) 5br] Under Mild Reaction Conditions

Carbon dioxide hydrosilylation with earth-abundant transition-metal catalysts is an attractive alternative for the design of greener and cost-effective synthetic strategies. Herein, simple [Mn(CO)₅Br] is an efficient precatalyst in the hydrosilylation of carbon dioxide with Et₃SiH under mild reaction conditions. Using THF as a solvent, triethylsilylformate Et₃SiCH(O)O was obtained in 67% yield after 1 hour at 50 °C and 4 bar of CO₂ pressure. The selectivity of the reaction was tuned by changing the solvent to a mixture of THF and toluene producing bis(triethylsilyl)acetal (Et₃SiO)₂CH₂ in 86% yield. The CO₂ hydrosilylation was also effective at room temperature and atmospheric pressure using either THF or the mixture THF/toluene as the solvent resulting in high Et3SiH conversion (92% - 99%) but with a decrease in the selectivity. Radical trapping experiments indicated the participation of radical species in the catalytic mechanism. To the best of our knowledge, this is the first report on CO₂ hydrosilylation catalyzed by transition-metal radical intermediates.