COMPLEXES CONTAINING HETERONUCLEAR QUADRUPLE BONDS - PREPARATION AND CHARACTERIZATION OF ALPHA-MO4WCL4(L-L)2 (L-L= DPPE, DMPE) AND BETA-MO4WCL4(L-L)2 (L-L = DPPM, DMPM, DPPE)

The quadruply bonded heterobimetallic complexes Mo-(4)WCl4(mu-dppm)2.2THF.C6H6 (1), beta-Mo-(4)WCl4 (mu-dppe)2 (2), alpha-Mo-(4)WCl4(dppe)2 (5), Mo-(4)WCl4(mu-dmpm)2 (3), and alpha-Mo-(4)WCl4(dmpe)2.4CH2Cl2 (4) are formed in the reactions between Mo-(4)WCl4(PMePh2)4 and bis(diphenylphosphino)methane (dppm), bis(diphenylphosphino)ethane (dppe), bis(dimethylphosphino)methane (dmpm), or bis(dimethylphosphino)ethane (dmpe), respectively. These complexes are the first examples of heteronuclear quadruply bonded complexes of the form M-(4)M'Cl4(L-L)2, where L-L groups are bidentate phosphines. Complexes designated alpha have chelating diphosphine ligands and complexes designated beta have bridging diphosphine ligands. Complexes 1 and 2 cocrystallize with small amounts of Mo-(4)MoCl4(mu-dppm)2 or alpha-Mo-(4)MoCl4(dppe)2 forming solid solutions. The apparent Mo-W distances are 2.2110 (7) angstrom for Mo-(4)WCl4(mu-dppm)2 and 2.234 (1) angstrom for beta-Mo-(4)WCl4(mu-dppe)2. Complexes 3 and 4 are free from contamination by their dimolybdenum analogs, and the Mo-W distances are 2.193 (2) angstrom for Mo-(4)WCl4(mu-dmpm)2 and 2.243 (1) angstrom for alpha-Mo-(4)WCl4(dmpe)2. In addition to the structural data for these complexes, each has been fully characterized using (P{H})-P-31-H-1 NMR and H-1 NMR spectroscopy. Complexes 1-5 all have methylene or ethylene protons located at positions that allow the calculation of the diamagnetic anisotropy of the Mo-(4)W bond from the H-1 NMR chemical shift data. The crystal structures of 1, 2, and 4 are fully described. Crystallographic data for these compounds are as follows: 1, P2(1)/c with a = 21.562 (3) angstrom, b = 14.567 (4) angstrom, c = 22.063 (4) angstrom, beta = 118.82 (1)-degrees, V = 6071 (2) angstrom3, Z = 4; 2, P2(1)/n with a = 23.099 (4) angstrom, b = 13.284 (1) angstrom, c = 16,765 (3) angstrom, beta = 107.45 (2)-degrees, V = 4894 (2) angstrom3, and Z = 4; 4, P2(1)/c with a = 10.422 (6) angstrom, b = 16.707 (6) angstrom, c = 11.406 (8) angstrom, beta = 111.87 (6)-degrees, V = 1843 (2) angstrom3, and Z = 2.