Formation of a zwitterionic boronium species from the reaction of a stable carbenoid with borane: CO2 reduction.

The treatment of Li2C(PPh2NMes)2 (1, Mes = 2,4,6-Me3C6H2) with hexachloroethane yielded the corresponding carbenoid 2 in good yields. The reactivity of 2 was studied with BH3·SMe2 to give a zwitterionic boronium species 4, also a stable carbenoid. Both carbenoid species were found to be excellent catalysts for the CO2 reduction by BH3·SMe2.