EDGE-SHARING BIOCTAHEDRAL DIMOLYBDENUM AND DIRHENIUM COMPOUNDS WITH POLYDENTATE PHOSPHINES

The edge-sharing bioctahedral (ESBO) compounds 1,2,7,8-Mo2Cl6(meso-eLT TP).C6H6 (2), (eLTTP = ,2,5,6-meso-Mo2Cl4[Et2PCH2CH2P(Ph)CH2P(Ph)]2.2C 6H6 (4),1,2,7,8-Re2-Cl6(meso-tetraphos-1) (5) (tetraphos-1 = Ph2PCH2CH 2P(Ph)CH2CH2P(Ph)CH2CH2PPh2), and 1,2,7,8-Re2-Cl6(meso-tetraphos-1)-(C H3CH2)2O (6) have been synthesized and structurally determined, and th ey represent new isomeric forms for the Mo2(mu-Y)2X4P4 core. The M-M b ond distances are 2.746(1) angstrom for 1, 2.8312(3) angstrom for 4, a nd 2.625(1) angstrom for both 5 and 6, which all fall within the range established for Mo-Mo and Re-Re bonds in ESBO molecules containing Mo (III) and Re(III). The meso-eLTTP ligand adopts a bischelating/single- bridging coordination mode. The diphosphine-phosphido ligand Et2PCH2CH 2P(Ph)CH2P(Ph), which forms by P-C bond cleavage of the original eLTTP ligand with the elimination of one -CH2CH2PEt2 unit, adopts a bischel ating mode, with the phosphido phosphorus atom occupying the bridging position. The crystal structures of 2 and 4-6 are fully described. Cry stallographic data for these compounds are as follows: (2) space group P1BAR with a = 12.437(2) angstrom, b = 17.850(3) angstrom, c = 8.903( 1) angstrom, alpha = 101.69(1)-degrees, beta = 95.64(1)-degrees, gamma = 91.33(6), V = 1924.3(6) angstrom3, and Z = 2; (4) space group P1BAR with a = 11.255(3) angstrom, b = 12.374(4) angstrom, c = 10.290(4) an gstrom, alpha = 98.57(2)-degrees, beta = 96.08(2)-degrees, gamma = 109 .21(2), V = 1320(2) angstrom3, and Z = 1; (5) space group P2(1)/c with a = 10.234(2) angstrom, b = 24.908(7) angstrom, c = 17.889(4) angstro m, beta = 93.14(2)-degrees, V= 4553(3) angstrom3, and Z = 4; (6) space group Pbca with a = 26.519(5) angstrom, b = 26.335(4) angstrom, c = 1 3.976(2) angstrom, V = 9760(5) angstrom3, and Z = 4.