The crystal structure of “green” Cs2[VOF4(H2O)] and its relationship to “blue” Cs2[VOF4(H2O)]

Crystals of a second, “green” modification of Cs₂[VOF₄(H₂O)] were obtained from aqueous solution. Their crystal structure was studied on the basis of three-dimensional X-ray data. The structure is orthorhombic, a = 8.231(3), b = 10.323(3), c = 8.497(3) Å, V = 722.0ų, Z = 4, space group Ccmm. The final R and R_W were 0.035 and 0.048, respectively, for 421 independent reflections. As the already known “blue” modification, the present structure contains isolated, highly deformed octahedral [VOF₄(H₂O)]^2? ions with the oxygen atoms in trans positions. The cesium sublattice and the orientation of the anions to each other are completely different in both modifications. uv/VIS reflection, and ir and Raman spectra of both modifications are discussed.