HEXAVANADIUM POLYOXO ALKOXIDE ANION CLUSTERS - STRUCTURES OF THE MIXED-VALENCE SPECIES (ME3NH)[V(IV)5V(V)O7(OH)3(CH3C(CH2O)3)3] AND OF THE REDUCED COMPLEX NA2[V(IV)6O7(CH3CH2C(CH2O)3)4]

While the hexametalate core {M6O19} is well-documented in the chemistry of the early transition metals, variable substitution of cluster oxo groups by common organic ligands and isolation of clusters with several reduced metal centers have remained elusive. As illustrated in the accompanying figure, the hexametalate core can accommodate up to four tridentate ligands spanning the triangular faces of the tetrahedral cavities of the superoctahedron. By employment of the techniques of hydrothermal synthesis, a series of sequentially substituted clusters, possessing variable electron populations, namely, [V(v)6O13{RC(CH2O)3}2]2-, [V(IV)5V(v)O7(OH)3-{RC(CH2O3}3]-, and [V(IV)6O7{RC5(CH2O)3}4]2-, have been prepared and structurally characterized.