Zirconium and hafnium aqua complexes [(H2O)3M(P2W17O61)]6−: Synthesis, characterization and substitution of water by chiral ligand

The hydroxocomplexes [{(H2O)M(μ2-OH)(P2W17O61)}2]14− (M = Zr, Hf) in HCl undergo cleavage of the hydroxo bridges with the formation of monomeric species [(H2O)3M(P2W17O61)]6−. In the case of Hf single crystals of the composition (Me2NH2)5.5(H)1.5[(Hf(H2O)3)0.9(WO)0.1{P2W17O61}]Cl·9.5H2O (1), as the result of co-crystallization of [(H2O)3Hf(P2W17O61)]6− and [P2W18O62]6− salts, were isolated from these solutions and structurally characterized. Zr gives (Me2NH2)2(H)4[{(H2O)2ZrP2W17O61}]·8.67H2O (2), in whose structure chiral polymeric chains {[(H2O)2M(P2W17O61)]}n6n− are present. Under hydrothermal conditions the water molecules in [(H2O)3M(P2W17O61)]6− are replaced by l-malic acid with the formation of stable chiral polyoxoanions, isolated as (NH2Me2)8[M(L-ООССН(ОН)СН2СОО)P2W17O61]·7·9H2O (M = Zr, 3; M = Hf, 4). The structures of 1, 2 and 3 were determined; 3 and 4 were found to be isostructural. The products were also characterized by elemental analysis, thermogravimetry and IR-spectroscopy.