INTERACTIONS OF COINAGE-GROUP CATIONS WITH THE TETRASELENOTUNGSTATE ANION - MULTINUCLEAR NMR SPECTROSCOPIC RESULTS AND CRYSTAL-STRUCTURES OF (MU-WSE4)[(PME2PH)2CU]2, (MU-WSE4)[(PMEPH2)AU]2, AND (MU-3-CL)(MU-3-WSE4)[(PPH3)CU]3

Reaction of a CH3CN solution of [NPr4]2[WSe4] with 2 equivalents of Cu+, Ag+, or Au+ in the presence of excess PMe2Ph affords (mu-WSe4)[(PMe2Ph)2M]2 (MCu(1),Ag(2), or Au(3)). (mu-WSe4)[(PMe2Ph)2Cu]2 crystallizes with four formula units in the monoclinic space group C2h6-C2/c in a cell of dimensions a = 19.315(7) angstrom, b = 15.575 (4) angstrom, c = 16.829 (7) angstrom, and beta = 127.99 (1)-degrees (T = 113 K). Full anisotropic refinement of the structure led to a value of R(F) = 0.032 (R(w)(F) = 0.042) for 196 variables and 4047 unique reflections. The molecule possesses a crystallographic 2-fold axis; the W center is tetrahedrally coordinated to four Se atoms that bridge to the Cu atoms; coordination of each Cu atom to two P atoms completes the distorted tetrahedral geometry about each Cu atom. Substitution of PMePh2 for PMe2Ph with M = Au+ affords (mu-WSe4)[(PMePh2)Au]2(4). This compound crystallizes with four molecules in the monoclinic space group P2(1)/c in a cell of dimensions a = 14.647 (5) angstrom, b = 14.161 (5) angstrom, c=15.319(6) angstrom, and beta = 106.65(1)-degrees (T = 113 K). A value of R(F) = 0.088 (R(w)(F) = 0.081) for 186 variables and 5859 unique reflections was obtained from anisotropic refinement of the heavy atoms. The structure is similar to that of 1, except that the geometry around the Au atoms is distorted trigonal planar. The Se-77 NMR spectra of solutions of 1-4 exhibit a single peak; for 1-3 this peak shifts to lower field with increasing atomic number of the coinage metal. The P-31 NMR spectra also consist of a single resonance. Reaction of [NPr4]2[WSe4] with [(PPh3)2Cu(BH3)(CN)]2 in CH2Cl2 in the presence of NH4Cl affords the cubane-like compound (mu3-Cl)(mu3-WSe4)[(PPh3)Cu]3 (5). Its structure, which has analogues in the MoSe42- and the WS42- systems, is that of a cubane in which each Cu center is bonded tetrahedrally to a P atom, a Cl atom, and two Se atoms and the W center is bonded tetrahedrally to four Se atoms. Consistent with this solid-state structure, the Se-77 NMR spectrum of a solution of 5 displays two resonances at delta 1651 and 1232 ppm. The compound crystallizes with four molecules in the orthorhombic space group D2(4)-P2(1)2(1)2(1) in a cell of dimensions a = 12.88 (1) angstrom, b = 17.72 (1) angstrom and c = 22.59 (1) angstrom (T = 113 K). The structure has been refined anisotropically to a value of R(F) = 0.063 (R(w)(F) = 0.069) for 570 variables and 8950 observations.