VANADIUM(V) PROTEIN MODEL STUDIES - SOLID-STATE AND SOLUTION STRUCTURE

The structures of oxovanadium(V) triethanolaminate, 1, and oxovanadium(V) tri-2-propanolaminate, 2, have been determined. In each case the V(V) atom exhibits distorted trigonal bipyramidal coordination with the nitrogen atom and the oxo group in the axial positions. The distortion is observed because the vanadium atom is displaced out of the plane of the triethanolaminate oxygens in the direction of the doubly-bonded oxygen. Compound 1 crystallizes in the monoclinic space group P2(1) with a = 7.051(2) angstrom, b = 7.429(2) angstrom, c = 7.980(2) angstrom, beta = 93.46(3)degrees, V = 417.2(2) angstrom3, and Z = 2. The discrete complex exhibits a V-N bond length of 2.276(1) angstrom and an average VO(C) bond length of 1.794(3) angstrom. Compound 2 crystallizes in the hexagonal space group P6(3) with a = 9.465(2) angstrom, c = 7.493(2) angstrom, V = 581.3(2) angstrom, and Z = 2. The discrete complex exhibits a V-N bond length of 2.297(15) angstrom and a VO(C) bond length of 1.794(5) angstrom. The multinuclear solution NMR parameters of 1 and 2 were determined and compared to the parameters for aqueous complexes of vanadate and triethanolamine and vanadate and tri-2-propanolamine, respectively. The results and analyses of these systems lead to structural characterization of the aqueous complexes. C-13 NMR and multinuclear NMR studies of related vanadium(V)-peptide complexes should assist in characterizing the coordination chemistry about the vanadium in complexes that resist structural analysis by X-ray diffraction.