Reactivity of an N-Heterocyclic Carbene Stabilized Hydrosilylene towards a Ketone and CO2: Experimental and Theoretical Study

The reaction of N-heterocyclic carbene (NHC)-stabilized hydrosilylene 1, tBu₃SiSi(H)←NHC, with one and two equivalents of benzophenone gave rise to bicyclic compounds 2 and 3, tBu₃Si(R)[Si-CH₂-N(CMeCMeNMe)-CPh₂-O] (R = H, OCHPh₂). The NHC plays a crucial role in this reactivity, as it is directly involved in C–C bond formation and supplies the C–H-activated methyl group. In the formation of 3, the terminal Si–H bond of the hydrosilylene is involved in transition-metal-free hydrosilylation. All steps in these mechanisms are based on NHC-stabilized zwitterionic transition states and intermediates and were investigated by utilizing DFT calculations. In addition, the CO₂activation of 1 to yield cis/trans-cyclotrisiloxane 4, [(tBu₃Si)(H)Si-O]₃, stereoselectively and its mechanistic study are reported.