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??-bipy?₂?C₆H₅PO₃?₂Mo5O15]n?1?,[?Cu?H2O?2?2??-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.