American Chemical Society
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Preparation, Structure, and Properties of Tetranuclear Vanadium(III) and (IV) Complexes Bridged by Diphenyl Phosphate or Phosphate

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journal contribution
posted on 2012-05-07, 00:00 authored by Kyouhei Sato, Tetsuya Ohnuki, Haruka Takahashi, Yoshitaro Miyashita, Koichi Nozaki, Kan Kanamori
Three novel tetranuclear vanadium­(III) or (IV) complexes bridged by diphenyl phosphate or phosphate were prepared and their structures characterized by X-ray crystallography. The novel complexes are [{V­(III)2(μ-hpnbpda)}2{μ-(C6H5O)2PO2}2(μ-O)2]·6CH3OH (1), [{V­(III)2(μ-tphpn)­(μ-η3-HPO4)}2(μ-η4-PO4)]­(ClO4)3·4.5H2O (2), and [{(V­(IV)­O)2(μ-tphpn)}2(μ-η4-PO4)]­(ClO4)3·H2O (3), where hpnbpda and tphpn are alkoxo-bridging dinucleating ligands. H3hpnbpda represents 2-hydroxypropane-1,3-diamino-N,N′-bis­(2-pyridylmethyl)-N,N′-diacetic acid, and Htphpn represents N,N,N′,N′-tetrakis­(2-pyridylmethyl)-2-hydroxy-1,3-propanediamine. A dinuclear vanadium­(IV) complex without a phosphate bridge, [(VO)2(μ-tphpn)­(H2O)2]­(ClO4)3·2H2O (4), was also prepared and structurally characterized for comparison. The vanadium­(III) center in 1 adopts a hexacoordinate structure while that in 2 adopts a heptacoordinate structure. In 1, the two dinuclear vanadium­(III) units bridged by the alkoxo group of hpnbpda are further linked by two diphenylphosphato and two oxo groups, resulting in a dimer-of-dimers. In 2, the two vanadium­(III) units bridged by tphpn are further bridged by three phosphate ions with two different coordination modes. Complex 2 is oxidized in aerobic solution to yield complex 3, in which two of the three phosphate groups in 2 are substituted by oxo groups.