Strandberg-type Organophosphomolybdates: Synthesis,Crystal Structures And Catalytic Properties

In this paper,chosing Na₂MoO₄·2H₂O as inorganic precursor,phenylphosphonic acid（C6H5PO3H2）as a P source,four Strandberg-type polyoxometalates（Polyoxometalates,abbreviated as POMs）modified by transition metal/organic moities were prepared under routine synthetic method and mild hydrothermal conditions.These compounds were characterized by single-crystal X-ray diffraction,elemental analysis,IR spectroscopy,TG-DTA analysis,and properties of fluorescent were also measured.Selecting the synthesis of cyclohexanone ethylene ketal as a model reaction,this kind of compounds was used as catalysts in organic synthetic reaction for the first time.Their acid catalytic performances were investigated systematically,which may lay a solid experimental foundation for the future research work.1.Three Strandberg-type organophosphomolybdates[（Cu（H₂O））₂（μ-bipy）₂（C₆H₅PO₃）₂Mo5O15]n（1）,[（Cu（H2O）2）2（μ-bipy）（C6H5PO3）2Mo5O15]n（2）and[（Ni（Hbipy）2（H2O）2）2(（C₆H₅PO₃）₂Mo₅O₁₅)₂·6H₂O]_n（3）were obtained in an aqueous soulution by self-assembly of simple oxysalt（Na₂MoO₄）,4,4’-bipyridy（4,4’-bipy）and transition metal(Cu²⁺and Ni²⁺).The Cu（II）/Ni（II）-bipy coordination groups were successfully introduced into the skeletons of polyoxoanions in compounds 1-3.2.A charge-transfer salt containing four protonated 2,2’-biimidazole（2,2’-biimidazole abbreviated as H₂biim）and one[Mo₅O₁₅（O₃PC₆H₅）₂]^4-was synthesized using a routine synthetic method,（H₃biim）₄[Mo₅O₁₅（O₃PC₆H₅）₂]·H₂O（4）.Compounds 1-4 used as acid-catalysts in an organic reaction with selecting the synthesis of cyclohexanone ethylene ketal as a model reaction.The performance of different reaction time,reactant ratio,catalyst dosage and reuse of catalyst were discussed with satisfactory results.The maximum yield of cyclohexanone ethylene ketal was about 96%,and the catalyst can be recycled.