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

Silyl triflates of the form R4-n Si(OTf)n (n=1, 2; OTf=OSO3 CF3 ) are shown to activate carbon dioxide when paired with bulky alkyl-substituted Group 15 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 R3 Si(OTf) reversibly bind CO2 affording [R'3 P(CO2 )SiR3 ][OTf] whereas when Ph2 Si(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.