Activation of Carbon Dioxide by Silyl Triflate-Based Frustrated Lewis Pairs

Silyl triflates of the form R4-nSi(OTf)(n) (n=1, 2; OTf=OSO3CF3) are shown to activate carbon dioxide when paired with bulky alkyl-substituted Group15 bases. Combinations of silyl triflates and 2,2,6,6-tetramethylpiperidine react with CO2 to afford silyl carbamates via a frustrated Lewis pair-type mechanism. With trialkylphosphines, the silyl triflates R3Si(OTf) reversibly bind CO2 affording [R3P(CO2)SiR3][OTf] whereas when Ph2Si(OTf)(2) is used one or two molecules of CO2 can be sequestered. The latter bis-CO2 product is favoured at low temperatures and by excess phosphine.