Zigzag Chain, Square Tetranuclear, and Polyoxometalate-Based Inorganic-Organic Hybrid Compounds - Molybdenum vs Tungsten

Substitution of the acetylacetonate ligands in [MO2(acac)(2)] (M = Mo or W; acac = acetylacetonate) by 2-oxy-1-naphthaldehyde izonicotinoyl hydrazonate (NIH2-) or 3-methoxy-2-oxybenzaldehyde izonicotinoyl hydrazonate (VIH2-) gives rise to either zigzag chain polymers, [MO2(NIH)](n) (1 and 2), square complexes [MO2(VIH)](4) (3 and 4), mononuclear complexes [MO2(VIH)(C2H5OH)] (5 and 6), to polyoxomolybdate hybrid compounds [{MoO2(HNIH)}(2)Mo6O19] (7) and [MoO2(HVIH)(H2O)](2)Mo6O19(8), depending on the reaction conditions. In all of these compounds, the ligand is coordinated to the CiS-MO22+ core via phenolic-oxygen, azomethine-nitrogen and enolic-oxygen atoms, while the remaining sixth coordination site is occupied by the nitrogen atom of the izonicotinyl part, or by an oxygen atom from the solvent molecule, or by an oxygen atom from the hexanuclear anion. Crystal and molecular structures of the molybdenum(VI) compounds [MoO2(NIH)](n) (1), [MoO2(VIH)](4) (3), [{MoO2(HNIH)}(2)Mo6O19] (7), and [MoO2(HVIH)(H2O)](2)Mo6O19 (8) were determined by the single crystal X-ray diffraction method. Dioxotungsten(VI) compounds [WO2(VIH)](n) (2) and [WO2(VIH)](4) (4) were structurally characterized by the X-ray powder diffraction method. All of the investigated compounds Were further characterized by elemental analysis, thermogravimetric analyses, cyclic voltammetry, FT-IR, UV-vis, and NMR spectroscopy.