CHEMISTRY OF THE WSE(4)2- ANION - SYNTHESIS, NMR-SPECTROSCOPY, AND CRYSTAL-STRUCTURE OF THE SELENIUM INSERTION PRODUCT [NET4]2[MU-WSE4][(SC4H3)SECU]2

Reaction of a CH3CN solution of [NEt4]2[WSe4] With 1 equiv of lithium (2-thienyl)cyanocuprate, Li[(CN)Cu(C4H3S)], affords [NEt4]2[mu-WSe4][(SC4H3)SeCu]2 (1), in which a Se atom from the decomposition of the WSe42- anion formally has been inserted into the 2-thienyl-copper bond Of CU(C4H3S) to form the 2-selenothiophene ligand. [NEt4]2[mu-WSe4][(SC4H3)SeCu]2 crystallizes with four formula units in the tetragonal space group D2d7 - P4b2BAR in a cell of dimensions a = 15.732(2) angstrom and c = 14.992(3) angstrom (T = 1 13 K). Full anisotropic refinement (4934 unique data, 173 variables) of the structure on F(o)2 led to a value of R(F) = 0.055 for those 4282 data having F(o)2 greater-than-or-equal-to 2sigma(F(o)2). The molecule has a crystallographically imposed 2-fold axis. Four Se atoms are arranged in an almost perfect tetrahedron about the W center; the Se atoms bridge to two Cu atoms, each of which in turn is bonded to a third Se atom in a distorted trigonal planar array. Each of these latter Se atoms is bonded to a thiophene group at the 2-position. The Se-77 NMR spectrum of a DMF solution of 1 exhibits two resonances at delta 905.8 and -18.1 ppm. The C-13 NMR spectrum displays six peaks at delta 15.5, 52.7, 65.9, 124.5, 127.9, and 131.6 ppm, consistent with the solid-state structure.