Synthesis, structure and characterization of a inorganic–organic hybrid Dawson polyoxotungstate (H2en)3[P2W18O62]·6.48H2O

A Dawson polyoxotungstate (H2en)3[P2W18O62]·6.48H2O 1 was prepared from the hydrothermal reaction of Na2WO4, CdCl2, H3PO4, ethylenediamine and H2O at 150 °C, and characterized by single crystal X-ray diffraction and spectroscopic methods. The compound crystallizes in the monoclinic system, space group P 2(1)/n with a=14.647(2), b=19.417(3), c=23.729(3) Å, β=95.116(3) °, Z=4, R1=0.0568 for 12645 observed reflections. The crystal is made up of [P2W18O62]6− Dawson anions, [H2en]2+ complex cations and H2O molecules of crystallization. The [H2en]2+ complex cations and Dawson anions are held together into a three-dimensional supermolecular network through hydrogen-bonding interactions. A probe reaction of the oxidation of cyclohexene into adipic acid with H2O2 as oxidation reagent and compound 1 as the catalyst showed that the hybrid material has a high oxidative activity in the reaction.