Wednesday, August 16, 2006

Sharon Ashbrook: 23Na MQMAS, Structure Determination via SSNMR and PXRD

Inorg. Chem., 45 (15), 6034 -6040, 2006. 10.1021/ic060483t S0020-1669(06)00483-6 Web Release Date: June 22, 2006 Copyright © 2006 American Chemical Society

Na2[(VO)2(HPO4)2C2O4]·2H2O: Crystal Structure Determination from Combined Powder Diffraction and Solid-State NMR

J. F. Colin, T. Bataille, S. E. Ashbrook, N. Audebrand, L. Le Pollès, J. Y. Pivan, and E. Le Fur*
Sciences Chimiques de Rennes, UMR 6226, CNRS-Université de Rennes 1-ENSCR, 35042 Rennes Cedex, France, and Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ, U.K.
Received March 22, 2006

Abstract: The vanadyl oxalatophosphate Na2[(VO)2(HPO4)2C2O4]·2H2O has been synthesized by hydrothermal treatment. Its structure has been determined and refined by combining X-ray powder diffraction and solid-state NMR techniques. It crystallizes with monoclinic symmetry in space group P21, a = 6.3534(1) Å, b = 17.1614(3) Å, c = 6.5632(1) Å, = 106.597(1). The structure is related to that of (NH4)2[(VO)2(HPO4)2C2O4]·5H2O, which was previously reported. The vanadium phosphate framework consists of infinite [(VO)(HPO4)] chains of corner-sharing vanadium octahedra and hydrogenophosphate tetrahedra. The oxalate groups ensure the connection between the chains to form a 2D structure. The sodium ions and the water molecules are located between the anionic [(VO)2(HPO4)2C2O4]2- layers. The thermal decomposition has been studied in situ by temperature-dependent X-ray diffraction and thermogravimetry. It takes place in three stages, where the first two correspond to water removal and the last to the decomposition of the oxalate group and water elimination, leading to the final product NaVOPO4.

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