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 CO2 activation of 1 to yield cis/trans-cyclotrisiloxane 4, [(tBu3Si)(H)Si-O]3, stereoselectively and its mechanistic study are reported.