Heterobinuclear Vanadium-Nickel Lantern-Type Complexes: Metal-Metal bonding and structure

Abstract

Heterobinuclear complexes with metal–metal bonds have been increasingly studied over the past two decades. Binuclear vanadium-nickel lantern-type complexes are studied here by density functional theory using the MN15-L functional. Three series of digonal, trigonal, and tetragonal lantern-type complexes VNiLx (x = 2, 3, 4) are treated, where the ligand L is formamidinate (fad), guanidinate (gua) and formate (OCHO). A trigonal complex with phosphinoamide ligands is also treated. Each complex is treated in three low-lying spin states to predict the ground state spin multiplicity. The V-Ni bond lengths obtained are noted with reference to the metal–metal formal bond order (fBO) values derived from molecular orbital analysis. Electron-bookkeeping diagrams derived from an electron counting strategy also yield V-Ni formal bond order values consistent with the V-Ni bond lengths and with the fBO values from MO analysis. The four ligands studied are compared with regard to their effects upon metal–metal bonding. The V-Ni bond lengths in these complexes, along with the V-Ni bond stretching frequencies, Wiberg bond index and formal shortness ratio values, are all categorized into ranges according to the V-Ni bond orders from zero to two.