Synthesis and structure of transition-metal-containing tungstomolybdosilic polyoxometalates and their catalytic performance in oxidation of cyclohexene with hydrogen peroxide

A series of title complexes with the general molecular formula, K ₄H₂[SiW₇Mo₄Me(H₂O)O ₃₉]·xH₂O (denoted as MeW₇; Me=Mn ²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn ²⁺, Cd²⁺), were synthesized. IR spectra, electronic spectra, XPS spectra and thermal analyses were systematically recorded. The crystal structure of MnW₇, determined from single-crystal X-ray diffraction at 293 K, belongs to the tetragonal system, space group P4/mnc, Z=2, a=1.4105(5) and c=1.2476(7)nm. These samples were investigated for the oxidation of cyclohexene with H₂O₂, and showed more activity than their corresponding parent compounds.