STRUCTURE DETERMINATION OF A COMPLEX PENTAMOLYBDODISULFATE FROM SYNCHROTRON-RADIATION LAUE DIFFRACTION PHOTOGRAPHS - DERIVATION AND APPLICATION OF A WAVELENGTH-DEPENDENT ABSORPTION CORRECTION

Laue diffraction photographs were recorded with the SRS wiggler beam at the SERC Daresbury Laboratory for small electrochemically grown crystals of uncertain composition. Diffraction intensities were obtained from these photographs and the structure successfully solved using direct methods, the cell dimensions and space group having been previously determined from weak diffractometer measurements and Weissenberg photography. The formula of the compound was found to be [Mo5S2O23]-[N(C2H5)4]4.C6H5CN, containing a sulfate analogue of a previously determined pentamolybdodiphosphate ion. Refinement converged initially at R = 0.131 for 2858 unique reflections, but subsequent application of a new Laue absorption correction procedure improved the data, allowing convergence at R = 0.107. Tetrakis(tetraethylammonium) pentamolybdodisulfate benzonitrile solvate, C39H85Mo5-N5O23S2, M(r) = 1535.9, monoclinic, P2(1)/n, a = 12.712 (5), b = 30.83 (2), c = 14.745 (6) angstrom, beta = 88.02 (1)-degrees, V = 5775.3 angstrom3, Z = 4, D(x) = 1.766 g cm-3, mu = 27.22 cm-1 at lambda = 0.5 angstrom, 42.89 cm-1 at lambda = 0.6 angstrom, 9.09 cm-1 at lambda = 0.65 angstrom and 22.83 cm-1 at lambda = 0.9 angstrom, F(000) = 3120, T = 298 K.