[C∧C∧C]-Type Pincer Carbene Complexes of Rhodium(III): Synthesis and Catalytic Applications

NHC pincers (NHC = N-heterocyclic carbene), which combine the structural benefits of both carbenes and pincer platforms, have shown diverse applications, spanning from fundamental organometallic chemistry to homogeneous catalysis. Although aryl-bridged bis(NHCs) represent the earliest developed and most studied type of NHC pincers, such [(CCC)-C-boolean AND-C-boolean AND]-platforms have been underutilized in the synthesis of rhodium complexes. In this study, we present several less explored organorhodium(III) complexes featuring [(CCC)-C-boolean AND-C-boolean AND]-pincers. Their synthetic route via a convenient oxidative addition approach has been explored, and the obtained cyclorhodium(III) complexes show versatile coordination geometry (square pyramidal or octahedral). Additionally, these cyclorhodium(III) complexes exhibit very different regioselectivity in catalytic alkyne hydrosilylations compared to known Rh(III) NHC catalytic systems. Finally, a few mechanistic studies have also been conducted, and a plausible mechanism was proposed.