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

摘要

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 chemicalstructures and geometries were determined by X-ray crystallography or spectral measurements. Vanadium(III) formedstructurally similar, oxo-bridged, dinuclear complexes with both ligands and exhibited intense absorption bands in thevisible 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 unitin the corresponding vanadium(III) dimer. The alkoxo group in all four complexes coordinated to a metal center in a protonatedform. The geometrical arrangements of the vanadium(IV)-Hbpmae and -Hbimae complexes were different witheach other. The intense absorption bands in the visible region of the oxo-bridged dinuclear vanadium(III) complexes wereassigned based on molecular orbital calculation.