Abstract
By controlling the pH of the reaction system, a dilacunary γ-Keggin silicotungstate [Cu(en)2(H2O)][H2en]{γ-SiW10O36[Cu(en)2(H2O)]2}·7.5H2O (1) (en = ethylenediamine) has been hydrothermally synthesized by the reaction of CuCl2 with α-H4SiW12O40 and characterized by IR spectra, thermogravimetric analysis, and single-crystal X-ray diffraction. The product is prepared in the pH range 7.9–8.2, which reveals that pH plays a key role in the assembly of saturated α-H4SiW12O40 to dilacunary [γ-SiW10O36]8− polyoxometalate. The polyoxoanion {γ-SiW10O36[Cu(en)2(H2O)]2]}4− of 1 presents a rare [γ-SiW10O36]8−-retaining structure, in which two lacunary sites of [γ-SiW10O36]8− are unoccupied, meanwhile, two [Cu(en)2(H2O)]2+ groups are grafted on either side of the [γ-SiW10O36]8− unit by Cu–O–W bond.
Acknowledgments
This work was supported by the Natural Science Foundation of China, Special Research Fund for the Doctoral Program of Higher Education, Innovation Scientists and Technicians Troop Construction Projects of Henan Province, the National Science Fund for Young Scholars of China (no. 21101059) and the Open Research Fund of State Key Laboratory of Inorganic Synthesis and Preparative Chemistry (grant no. 2011-26).