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 (PCP)-P-BIm 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 [mu-OCH3Rh(COD)](2) smoothly forming the target organometallics [(PCPPdCl)-P-BIm][PF6] and [(PCPRh)-P-BIm(L)][PF6] under mild hydrogenation conditions. A more detailed study of the rhodium complexes [(PCPRh)-P-BIm(L)][PF6] reveals significant thermal stability of the (PCPRh)-P-BIm 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 (PCPRhI)-P-BIm complex is a sufficiently stable compound, with the potential to be applied in catalysis.