Hydrothermal synthesis and characterization of (N(C2H5)4)4[VMo12V2O44]

The hydrothermal reaction of a mixture of Na₂MoO₄·2H₂O, V₂O₅, pyromellitic acid (1,2,4,5‐C₆H₂(COOH)₄), (C₂H₅)₄NCl and 0,1 M H₂SO₄ for 88 h at 180°C gives blue needle‐like crystals of V^IV₂O₂(H₂O)₂ (C₆H₂(COO)₄)] in 20% yield (based on V) and dark blue prismatic crystals of the title compound, mixed‐valance (N(C₂H₅)₄)₄VMo₁₂V₂O₄₄], 1, in 12% yield (based on Mo). 1 was investigated by means of elemental analysis, thermogravimetry, Fourier Transform Infrared Spectroscopy and Single Crystal X‐ray Diffraction Methods. Crystal data for the compound: monoclinic space group P2₁/c (No:14), a=13.7815(12) b=13.0271(9) c= 21.189(2) Å, β= 113.909(7)°, Z=2. Although XM₁₄O₄₂]^‐n (X=P, Si, Ge, V and M=Mo and/or V) cores have been previously determined, this is the first time that VMo₁₂V₂O₄₄]^‐4 core is synthesized and characterized. The structural difference between 1 and these HPOMs is the coordinational geometry of the central metal atoms. The central vanadium in 1 has an octahedral coordination geometry, whereas in literature, the central V, P, Si and Ge atoms in V₁₅O₄₂]^‐9 / SiM₈V₆O₄₂]^‐4 / PM₈V₆O₄₂]^‐5 / GeM₈V₆O₄₂]^‐4 have tetrahedral coordinational geometry. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)