Synthesis, Structure And Catalytic Properties Of V/Mo/W Polyoxometalates Modified With Nitrogen-containing Ligands/metal Complexes

Polyoxometalates(POMs) as inorganic clusters that have particular structures and various properties have attracted many scientists. POMs have been utilized in host-guest chemistry, biochemistry, nanotechnology and electricity, magnetism and light chemical materials. Additionaly, POMs also as environment-friendly catalyst, have high activity,mild reaction conditions, and small corrosion.In this paper, three kinds of complexes were synthesized by transition metals ions,N-containing organic ligands and POMs. The crystal structures have been studied indetail,and the catalytical properties of some of complexes have also been researched. The main work is as follows:1. By regulating the initial reaction conditions, four transition metals modified polyoxovanadium clusters [TMAH]2[Mn(H2O)5]2[V10O28]·H2O(1),[TMAH]2[Zn(H2O)5]2[V10O28]·2H2O(2),[TEAH]2[Co(H2O)5]2[V10O28]·2H2O(3),[TMAH]2[Ni(H2O)5]2[V10O28]·2H2O(4)(TMAH = tetramethylammonium cation; TEAH =tetraethylammonium cation) have been synthesized. Complex 1-3 have good efficient and selective oxidation to catalyze various aromatic alcohols using molecular oxygen as the oxidant. Specifically, under un-optimized condition(acetonitrile as solvent, 2 atm O2pressure), complex 2 exhibits good efficiency in catalyze aromatic alcohols oxidized into corresponding aromatic ketones, con. 65.0%-67.0% and sele. 93.1%-98.9%. This phenomenon suggests that the kind of metal ion play a very important role during the catalytic reaction.2. A series of Keggin POM complexes modified by N-containing ligand or transition metal complex moiety have been obtained under hydrothermal condition: Keggin POMs modified by N-containing ligand(complex 5-6), classical Keggin POMs modified by transition metal complex moiety(complex 7-10), bi-capped Keggin POMs modified by N-containing ligand(complex 11) and bi-capped Keggin POMs modified by transition metal complex moiety(complex 12-21). Their catalytic performance in the selective oxidation of diphenyl methane is further investigated. The results show complex 13(H2[Cu L4][PMo5VMo7VIV2IVO42]·2H2O) have high activity in converting diphenyl methane oxidized into diphenyl ketone use under un-optimized condition(0.5 m L cyanobenzene as sovlent, 0.625 mmol t-butylhydroperoxide as the oxidantand, diphenyl methane 0.25 mmol,complex 13 25 mg as catalyzer and reacted at 80°C for 14 hours), con. 96.6% and sele.96.2%. It is revealed that the isostructural complexes show very different catalytic properties, kind of metal ion play a very important role during the catalytic reaction, the Cu ion possesses obvious superiority.3. The mixture of salicylhydroxamic acid(shi H3) and phosphomolybdate have reacted at room temperature and obtained three 18-MC-6 complexes:[La(Mo O2)6(shi)6][La(DMF)6(H2O)6](22), {[Ba3(DMF)8][(Mo O2)6(shi)6]}-(DMF)4(23),{[Ca3(DMF)8][(Mo O2)6(shi)6]}(DMF)4(24) and one octanuclear heterometal cluster[Ni6(Mo O2)2(shi)2Py8(H2O)2(μ2-O)2(Ac)4](25), which are characterized by single-crystal X-ray diffraction and elemental analysis. Studying the synthesis condition of complexes, it can be conclude that the polyoxomolybdate cluster are usually formed in hydrosolvent;while in non-aqueous solvent, the coordination complex containing Mo atoms can be obtained.