Toward New Organometallic Architectures: Synthesis of Carbene-Centered Rhodium and Palladium Bisphosphine Complexes. Stability and Reactivity of [PCBImPRh(L)][PF6] Pincers

In this article, we report the synthesis of a tridentate carbene-centered bisphosphine ligand precursor and its complexes. The developed four-step synthetic strategy of a new PCBImP pincer ligand represents the derivatization of benzimidazole in the first and third positions by (diphenylphosphoryl)­methylene synthone, followed by phosphine deprotection and subsequent insertion of a noncoordinating anion. The obtained ligand precursor undergoes complexation, with PdCl2 and [μ-OCH3Rh­(COD)]2 smoothly forming the target organometallics [PCBImPPdCl]­[PF6] and [PCBImPRh­(L)]­[PF6] under mild hydrogenation conditions. A more detailed study of the rhodium complexes [PCBImPRh­(L)]­[PF6] reveals significant thermal stability of the PCBImPRh moiety in the solid state as well as in solution. The chemical behavior of 1,3-bis­(diphenylphosphinomethylene)­benzimidazol-2-ylrhodium acetonitrile hexafluorophosphate has been screened under decarbonylation, hydrogenation, and hydroboration reaction conditions. Thus, the PCBImPRhI complex is a sufficiently stable compound, with the potential to be applied in catalysis.