AN X-RAY STUDY OF THE COMPLEX ANION BIS(N-HYDROXY-IMINODIACETATE)VANADATE(IV), A MODEL FOR A VANADIUM-CONTAINING BIOLOGIC COMPOUND

The structure of ammonium tetramethylammonium bis(N-hydroxy-iminodiacetate)vanadate(IV) was determined by x-ray analysis. One independent anion and two cations were found in the asymetric unit. The crystal is monoclinic. space group C2/c, with a = 15.820(9), b = 16.450(6), c = 16.311 (4) angstrom, beta = 118.92(3) deg., V = 3715(3) angstrom3, Z = 8, D(x) = 1.56g cm-3, mu(M(o)-K(a)) = 5.59 cm-1, F(000) = 2028, M = 434.9 for C12H24N4O10V. The structure was solved and refined to R(F) = 0.029 and R(W)(F) 0.040. The complex anion does not contain the oxovanadium(IV) group, but contains vanadium(IV) as the central atom. This is the first example of a vanadium(IV) complex octacoordinated to nitrogen and oxygen atoms exhibiting a highly distorted dodecahedral geometry. The chelation is along two a and four g edges. As the angles ones are bonding distances (N-O, 1.381(3), 1.382(4) angstrom) the angles around the central atom are very different from those usually observed in the dodecahedral complexes. The V-O distances range from 1.973(3) to 2.071(3) angstrom and the V-N distances range from 2.002(3) to 2.003(4) angstrom.