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The authors' review compiles the literature in the field of polyoxomolybdates, POMo, and polyoxomolybdovanadates, POMoV, over the past two decades. The main achievements in the field of synthesis, crystal and molecular structure determinations and applications are presented. The first section describes polyoxomolybdates; their structure starting with a smaller number of building units to the formation of new structural shapes of polyoxomolybdate clusters of supramolecular arhitecture. Polyoxo-molybdates include the compounds with various organic ligands, functionalized polyoxomolybdates and a number of organo-inorganic clusters. Recent synthetic methods such as functionalization and hydrothermal/solvothermal synthesis with a possibility to control the size and shape of the resulting structure are reviewed. The design and synthesis of inorganic-organic hybrid compounds in which POMo anions are combined with organic molecular cations appears as the most successful approach for preparing novel types of molecular based materials with functional properties. The second section covers the polyoxo-molybdovanadate compounds from structure to synthesis. Interesting compounds with the molybdenum- rich region or vanadium rich-region, mixed vanadium-molybdenum polyoxoanions with various oxidation states of the metal atoms and the organic-inorganic hybrid materials are described. The last section reviews the application of the before mentioned compounds. Due to the functionalization of the complexes potential utility in biology and medicine, catalysis and material science is significantly increased. Finally, the importance of large polyoxometalate clusters as target nanosized molecular materials, which present a challenge for the future complex chemistry, is discussed.

The synthesis of two monomeric molybdenum(VI) Schiff base complexes derived from N-phenyl-2-hidroxy-1-naphthaldimine and N-benzyl-2-hidroxy-1-naphthaldimine: [MoO2(C5H7O2)(OCH3)(2-OC10H6CH=NHC6H5)] (I) and [MoO2(C5H7O2)(OCH3)(2-OC10H6CH=NHCH2C6H5)] (II) described in this paper are the first examples in which potentially bidentate Schiff bases are monodentately bonded to molybdenum as zwitterionic ligands. The structure of complex I was determined by X-ray analysis. Within the same ligand, the hydrogen atom attached to nitrogen forms an intramolecular hydrogen bond of 2.548(2) Å with the oxygen atom coordinated to molybdenum. The octahedral coordination of molybdenum is completed by two oxo-oxygens, two acetylacetonato oxygens and one methoxy oxygen. The compounds were characterized by chemical analysis, IR spectroscopy and single crystal structure determination.

In the reaction of tris(2, 4-pentandionato)vanadium(III) with salicylaldehyde 4-phenylthiosemicarbazone (in complex 1) and 3-methoxy-salicylaldehyde 4-phenylthiosemicarbazone (in complex 3), two new mononuclear complexes of vanadium(V), [VO(SNO)(OCH3)] (1, 3) and thiazoline derivatives, {; ; ; ; ; ; R-CHNN[CNC(C6H5)C(CH3)C(O)(CH3)S]}; ; ; ; ; ; [R = -C6H4(OH) (L1cycl, 2) or -C6H3(OCH3)(OH) (L2cycl, 4)] have been prepared. The isolation of the thiazoline derivatives is the first example of cyclization reactions of thiosemicarbazones with an appropriate β -diketone involving vanadium. In vanadium(V) complexes, 1 and 3 vanadium is coordinated by one doubly bonded oxygen atom, ONS atoms from the salicylaldehyde thiosemicarbazone ligand and by an oxygen atom from methoxo ligand. All compounds have been characterized by means of chemical analyses and IR spectroscopy. The crystal and molecular structures of 1-4 have been determined by single-crystal X-ray diffraction method.

Visualization and Inspection of Electron Density Maps in Small Molecule Crystallography