Octaboraneyl Complexes of Nickel: Monomers for Redox‐Active Coordination Polymers
Marcus W. Drover, Maeve C. Dufour, Lindsay A. Lesperance‐Nantau, Rayni P. Noriega, Kirill Levin, Robert W. Schurko
Abstract
Abstract Herein, we establish the preparation, characterization, and reactivity of a new diphosphine ligand, 1,2‐bis(di(3‐dicyclohexylboraneyl)propylphosphino)ethane (P 2 B Cy 4 ), a scaffold that contains four pendant boranes. An entryway into the coordination chemistry of P 2 B Cy 4 is established by using nickel, providing the octaboraneyl complex [Ni(P 2 B Cy 4 ) 2 ]—this species contains a boron‐rich secondary coordination sphere that reacts readily with Lewis bases. In the case of 4,4′‐bipyridine, an air‐sensitive coordination polymer is obtained. Characterization of this material by solid‐state NMR and EPR spectroscopy reveals the presence of a charge‐transfer polymer, which forms as a function of intramolecular Ni→4,4′‐bpy electron transfer (ET), providing an array of oxidized nickel sites and reduced 4,4′‐bpy radical anion sites. Notably, the related intermolecular reaction between the model fragments [Ni(d n ppe) 2 ] (d n ppe=1,2‐bis(di‐ n ‐propylphosphino)ethane) and a bis(boraneyl)‐protected 4,4′‐bpy, provides no ET. Overall, the P 2 B Cy 4 fragment provides a unique opportunity for Lewis base activation, in one case allowing for the facile construction of monomers for incorporation into redox‐active macromolecules.