CRYSTAL-STRUCTURE OF CS4(VO)2O(SO4)4

Brownish yellow crystals of a V(V) compound, cesium (mu-oxo)bis(oxodisulfatovanadate)(-4), Cs4(VO)20(SO4)4, suitable for X-ray determination, have for the first time been obtained from the catalytically important Cs2S2O7/V2O5 system. By slow cooling of a mixture with the composition X(V2O5) = 0.251 from 380 (i.e. just below the liquidus temperature) to 350-degrees-C, the crystal growth could be promoted by the solid V2O5 present in the melt. The compound crystallizes in the triclinic space group P1BAR (No. 2) with a = 8.117(2) angstrom, b = 11.104(2) angstrom, c = 11.799(2) angstrom, alpha = 79.58(1)-degrees, beta = 87.95(2)-degrees, and gamma = 75.61(2)-degrees at 18-degrees-C and Z = 2. It contains two very similar distorted VO6 octahedra joint through corners corresponding to a V-O-V bridge with an angle of 165.3-degrees. Each octahedron exhibits a short V-0 bond of 1.58 angstrom and a longer bond of around 1.77 angstrom to the bridging oxide ion. The remaining four V-0 bonds are associated with two bidentate coordinated sulfate groups with three V-0 bonds in the range 1.86-2.02 angstrom and a long one around 2.40 anstrom trans to the short V-0 bond. The two equatorially coordinated bidentate sulfate groups are strongly distorted from the tetrahedral geometry-the O-S-0 angle being only approximately 97-degrees. This distortion may explain the shift and splitting of the sulfate P3 bands to unusual high wavenumbers-up to about 1300 cm-1-as observed in the IR spectra Of CS4(VO)20(SO4)4