SPECTROSCOPIC AND MAGNETOSTRUCTURAL CORRELATIONS IN OXE-BRIDGED DINUCLEAR VANADIUM(III) COMPLEXES OF POTENTIAL BIOLOGICAL SIGNIFICANCE

The synthesis of several dinuclear (mu-oxo)bis(mu-carboxylato or diphenylphosphato) divanadium(III) complexes, [V2O(O(2)CR)(2)L(2)] (where L = HB(pz)(3)(-) and R = CH3 (I), C6H5 (II), C2H5 (III), and H (IV), or L = HB(3,5-Me(2)pz)(3)(-) and R = CH3 (V) and [V2O(O2P(OC6H5)(2))(2)(HB(pz)3)(2)] (X), are described. X-ray crystallographic analysis of III and X gave the following parameters: III, C32H42B2N16O5V2, P2(1)/n, a = 13.406(3) Angstrom, b = 15.313(3) Angstrom, c = 22.217(4) Angstrom, beta = 106.75(3)degrees, Z = 4, V = 4367(2) Angstrom(3); X, C44H43B2N13O9P2V2, P2(1)/n, a 11.944(4) Angstrom, b = 20.091(7) Angstrom, c = 21.729(16) Angstrom, beta = 94.38(4)degrees, Z = 4, V = 5199(4) Angstrom(3). Protonation of the ore-bridged species with either HClO4 or HSO3CF3 causes a rapid color change from deep green to pale red and results in the crystallization of the hydroxo-bridged species [V-2(OH)(O(2)CR)2(HB(pz)3)2](X) (where R = CH3 and X = ClO4- (VI) or R = C2H5 (VII), C6H5 (VIII), and H (IX), and X = CF3SO3-) and [V-2(OH)(O2P(OC6H5)2)(2)(pz)3)2](CF3SO3) (XI). Crystallographic parameters are as follows: VIIb, C29H39B2F3N12O9SV2, P2(1)2(1)2(1), a = 12.309(3) Angstrom, b = 16.197(2) Angstrom, c = 20.232(2) Angstrom, Z = 4, V = 4033.9(9) Angstrom(3); XI, C(56.5)H(64.5)B(2)F(3)N1(2)O(14.5)P(2)SV(2), P (1) over bar, a 12.113(2) Angstrom, b = 14.938(3) Angstrom, c = 20.052(4) Angstrom, alpha = 72.88(3)degrees, beta = 76.73(3)degrees, gamma = 87.15(3)degrees, Z = 4, V = 3374.3(11) Angstrom(3). In contrast to well-studied ore-bridged Fe(III) complexes, UV-visible, paramagnetic NMR, resonance Raman, and magnetic susceptibility on these V(III) complexes reveal electronic and magnetostructural correlations dependent on the V-O-V angle. Such correlations may be useful in assigning structures to complex biosystems containing the [V(mu-O)V](4+) core.