Syntheses, Crystal Structures, NMR Spectroscopy, and Vibrational Spectroscopy of Sr(PO sub(3)F).H sub(2)O and Sr(PO sub(3)F)

Single crystals of Sr(PO sub(3)F).H sub(2)O {P2 sub(1)/c, Z = 4, a = 7.4844(2) Aa, b = 7.0793(2) Aa, c = 8.4265(2) Aa, beta = 108.696(1) degree , V = 422.91(2) Aa super(3), 2391 F sub(o) super(2), 70 parameters, R sub(1)[F super(2)> 2 sigma (F super(2))] = 0.036; wR sub(2)(F super(2) all) = 0.049, S = 1.054} were grown from an aqueous solution by a metathesis reaction. The structure comprises [SrO sub(8)] polyhedra and PO sub(3)F tetrahedra that form a layered arrangement parallel to (100). The topotactic dehydration of this phase proceeds between 80 and 140 degree C to afford Sr(PO sub(3)F). The monazite-type crystal structure of Sr(PO sub(3)F) was elucidated from the X-ray powder data by simulated annealing [P2 sub(1)/c, Z = 4, a = 6.71689(9) Aa, b = 7.11774(11) Aa, c = 8.66997(13) Aa, beta = 128.0063(7) degree , V = 326.605(8) Aa super(3), R sub(p) 0.010, R sub(w)p 0.015, R sub(F) 0.030]. During dehydration, the structure of Sr(PO sub(3)F).H sub(2)O collapses along [100] from a layered arrangement into a framework structure, accompanied by a change of the coordination number of the Sr super(2+) ions from eight to nine. The magic-angle spinning (MAS) NMR and vibrational spectroscopy data of both phases are discussed. The dehydration of Sr(PO sub(3)F).H sub(2)O yields Sr(PO sub(3)F) by a topotactic reaction. The crystal structures of both solids were elucidated by X-ray diffraction methods, and the presence of P-F bonds was confirmed by magic-angle spinning (MAS) NMR and IR spectroscopy.