Synthesis and Structures of Vanadium(III) and -(IV) Complexes with a Tripodal Quadridentate Ligand Containing Alcoholic and Pyridyl or Imidazolyl Functionality

Abstract

Abstract:Complexes of vanadium(III) and vanadium(IV) were synthesized with the tripodal quadridentate ligands, N,Nbis(2-pyridylmethyl)-2-aminoethanol (Hbpmae) and N,N-bis(2-imidazolylmethyl)-2-aminoethanol (Hbimae). The chemical structures and geometries were determined by X-ray crystallography or spectral measurements. Vanadium(III) formed structurally similar, oxo-bridged, dinuclear complexes with both ligands and exhibited intense absorption bands in the visible region. Upon exposure to air, the vanadium(III) complexes oxidized spontaneously, yielding the respective vanadium(IV) complexes. The geometry of the vanadium(IV)-Hbpmae complex was very similar to that of the monomeric unit in the corresponding vanadium(III) dimer. The alkoxo group in all four complexes coordinated to a metal center in a protonated form. The geometrical arrangements of the vanadium(IV)-Hbpmae and -Hbimae complexes were different with each other. The intense absorption bands in the visible region of the oxo-bridged dinuclear vanadium(III) complexes were assigned based on molecular orbital calculation.