Cooperative CO2 Scission by Anomalous Insertion into a Rh–Si Bond

Pincer-type [P2Si]Rh complexes featuring a rhodium–silicon bond are shown to facilitate well-defined stoichiometric reductions of CO2 with Si–O bond formation by two different pathways: (a) hydride transfer to CO2 followed by formate migration to silicon, or (b) complete scission of the C═O bond at the Rh–Si unit to afford a product with siloxide and carbonyl ligands. A combined experimental and computational study shows that the latter process occurs by anomalous insertion of CO2 into the polarized Rhδ−–Siδ+ bond, a finding that is confirmed by extending the reactivity to an unchelated system. The siloxide carbonyl product can be further elaborated by reaction with water or pinacolborane to give structurally distinct CO2 reduction products. Taken together, these results demonstrate how metal/main-group bonds can be tuned to direct migratory insertion reactivity.