HETEROBIMETALLIC EDGE-SHARING BIOCTAHEDRAL COMPLEXES - SYNTHESIS, CHARACTERIZATION, AND SINGLET TRIPLET SEPARATIONS AS DETERMINED BY P-31 NUCLEAR-MAGNETIC-RESONANCE

The heterobimetallic edge-sharing bioctahedral complexes MoWCl6(dppe)2 (1), MoWC16(mu-dppm)2 (2), and MoWCl6(mu-dmpm)2 (3) are formed as the oxidative addition products of the reaction between the corresponding quadruply bonded complex and PhICl2 or CH2Cl2. These complexes are the first examples of heteronuclear edge-sharing bioctahedral complexes of the form MM'Cl4(mu-Cl)2(L-L)2, where L-L are bidentate phosphines. Complex 2 cocrystallizes with small amounts of Mo2Cl6(mu-dppm)2 forming a solid solution. The apparent Mo-W distance is 2.7320(6) angstrom for MoWCl6(mu-dppm)2. Complexes 1 and 3 are free from detected contamination by their dimolybdenum analogs, and the Mo-W distances are 2.7123 (9) angstrom for MoWCl6(dppe)2 and 2.682 (1) angstrom for MoWCl6(mu-dmpm)2. In addition to the structural data for these complexes, each has been fully characterized using (P{H})-P-31-H-1 and H-1 NMR spectroscopy. Variable-temperature (P{H})-P-31-H-1 NMR spectroscopic studies were utilized to characterize the magnetic properties of 1-3 as well as the respective homonuclear complexes. Statistical analysis of the temperature dependence of the chemical shift allows the calculation of the singlet-triplet gap (2J), the hyperfine coupling constant (A), and the diamagnetic shift (delta(dia)). The crystal structures of 1-3 are fully described. Crystallographic data for these compounds are as follows: (1) P2(1)/n with a = 12.785 (3) angstrom, b = 12.286 (3) angstrom, c = 17.774 (2) angstrom, beta = 108.598 (1)-degrees, V = 2653 (2) angstrom3, and Z = 2; (2) C2/c with a = 23.030 (3) angstrom, b = 10.904 (2) angstrom, c = 23.2221 (3) angstrom, beta = 124.147 (8)-degrees, V = 4826 (1) angstrom3, and Z = 4; (3) P2(1)/c with a = 7.0178 (9) angstrom, b = 15.526 (2) angstrom, c = 10.993 (2) angstrom, beta = 94.346 (6)-degrees, V = 1187.9 (9) angstrom3, and Z = 2.