HYDROTHERMAL SYNTHESIS AND CHARACTERIZATION OF HEXAVANADIUM POLYOXO ALKOXIDE ANION CLUSTERS - CRYSTAL-STRUCTURES OF THE VANADIUM(IV) SPECIES BA[V6O7(OH)3((OCH2)3CCH3)3].3H2O AND NA2[V6O7((OCH2)3CCH2CH3)4], OF THE MIXED-VALENCE COMPLEX (ME3NH)[VIV5VVO7(OH)3((OCH2)3CCH3)3], AND OF THE FLUORO DERIVATIVE NA[V6O6F(OH)3((OCH2)3CCH3)3].3H2O

The hydrothermal reactions of vanadium oxide precursors with trialkoxy ligands of the class (HOCH2)3CR (R = CH3, CH2CH3) yield polyalkoxyoxovanadium clusters with a hexametalate core, Ba[V607(OH)3{(OCH2)3-CCH3}3].3H2O (1), Na2[V607{(OCH2)3CCH2CH3}4] (2), (Me3NH)[V607(OH)3{(OCH2)3CCH3}3] (3), and Na-[V606F(OH)3{(OCH2)3CCH3}3].3H20(4). Cluster 1 is a fully-reduced V(IV) species in which nine doubly bridging oxo groups of the parent {V6019} core have been substituted by alkoxy oxygen donors of the three trialkoxy ligands. The structure of 3 is grossly similar to that of 1, with differences in metrical parameters reflecting the presence of one oxidized V(V) site in the metal core of 3. The fully reduced cluster 2 exhibits complete substitution of the doubly-bridging oxo groups of the parent core by 12 ligand alkoxy donors. The tendency of polyvanadium oxide clusters to encapsulate a variety of guest molecules or ions is demonstrated by the structure of 4, in which the central mu6-Oxo group of the parent core has been substituted by a mu3-fluoride, resulting in a considerably distorted {V6O6-(mu3-F)(A2-OH)3(mu2-OR)9} core. Crystal data for 1: hexagonal space groUP P63mc, a = 13.707(l) angstrom, c = 9.647(2) angstrom, v = 1569.7(2) angstrom3, Z = 2, D(calc), = 2.140 g CM-3; Structure solution and refinement based on 399 reflections converged at R = 0.0576. Crystal data for 2: cubic space group Fd3, a = 19.202(4) angstrom, V = 7080(1) angstrom3, Z = 8, D(calc) = 1.749 g CM-3; 293 reflections, R = 0.0509. Crystal data for 3: hexagonal space group P63mc, a = 12.792(3) angstrom, c = 10.692(2) angstrom, V = 1515.2(6) angstrom3, Z = 2, D(calc) = 1.929 g cm-3; 651 reflections, R = 0.0410. Crystal data for 4: hexagonal space group P6(3)mc, a = 12.977(l) angstrom, c = 10. 16o(i) angstrom, V = 1481.7(2) angstrom3, Z = 2, D(calc) = 2.020 g CM-3; 379 reflections, R = 0.0371.