Preparation, Structure,
and Properties of Tetranuclear Vanadium(III) and (IV) Complexes Bridged
by Diphenyl Phosphate or Phosphate
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Abstract
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)<sub>2</sub>(μ-hpnbpda)}<sub>2</sub>{μ-(C<sub>6</sub>H<sub>5</sub>O)<sub>2</sub>PO<sub>2</sub>}<sub>2</sub>(μ-O)<sub>2</sub>]·6CH<sub>3</sub>OH (<b>1</b>), [{V(III)<sub>2</sub>(μ-tphpn)(μ-η<sup>3</sup>-HPO<sub>4</sub>)}<sub>2</sub>(μ-η<sup>4</sup>-PO<sub>4</sub>)](ClO<sub>4</sub>)<sub>3</sub>·4.5H<sub>2</sub>O (<b>2</b>), and [{(V(IV)O)<sub>2</sub>(μ-tphpn)}<sub>2</sub>(μ-η<sup>4</sup>-PO<sub>4</sub>)](ClO<sub>4</sub>)<sub>3</sub>·H<sub>2</sub>O (<b>3</b>), where hpnbpda and tphpn are alkoxo-bridging dinucleating
ligands. H<sub>3</sub>hpnbpda represents 2-hydroxypropane-1,3-diamino-<i>N,N′</i>-bis(2-pyridylmethyl)-<i>N,N′</i>-diacetic acid, and Htphpn represents <i>N,N,N′,N′</i>-tetrakis(2-pyridylmethyl)-2-hydroxy-1,3-propanediamine. A dinuclear
vanadium(IV) complex without a phosphate bridge, [(VO)<sub>2</sub>(μ-tphpn)(H<sub>2</sub>O)<sub>2</sub>](ClO<sub>4</sub>)<sub>3</sub>·2H<sub>2</sub>O (<b>4</b>), was also prepared
and structurally characterized for comparison. The vanadium(III) center
in <b>1</b> adopts a hexacoordinate structure while that in <b>2</b> adopts a heptacoordinate structure. In <b>1</b>, 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 <b>2</b>, the two vanadium(III) units
bridged by tphpn are further bridged by three phosphate ions with
two different coordination modes. Complex <b>2</b> is oxidized
in aerobic solution to yield complex <b>3</b>, in which two
of the three phosphate groups in <b>2</b> are substituted by
oxo groups
