COMPLEXES CONTAINING HETERONUCLEAR AND HOMONUCLEAR QUADRUPLE BONDS - PREPARATION AND CHARACTERIZATION OF MOWCL4(DMPM)2 AND MO2X4(DMPM)2 (X = BR, I)

The quadruply bonded heterobimetallic complex MoWCl4(dmpm)2 (1) and th e homobimetallic complexes Mo2X4-(dmpm)2 (X = Br (2),I, (3)) were synt hesized and their structures determined. The crystals of compound 1 ex hibit the typical disorder for heteronuclear systems, namely, the rand om orientation of the M-M' vector, with each metal atom appearing as 5 0% Mo and 50% W. The structural refinement in the space group P4 resul ted in lower residuals, with R = 0.048 and R(w) = 0.067, than in the s pace group P4/m. For complexes 2 and 3, crystals obtained from THF sol utions are monoclinic, with space groups P2(1)/c and P2(1)/n for 2 and 3, respectively. The quadruple bond distances are 2.193(2), 2.1271 (8 ), and 2.132(2) angstrom for 1, 2, and 3, respectively. In addition, e ach complex has been characterized using UV-visible, P-31{H-1} NMR, an d H-1 NMR spectroscopies. The average magnetic anisotropy of the Mo-Mo quadruple bond in complexes 2 and 3 has been calculated from H-1 NMR data as -4450 x 10(-36) m3 molecule-1. The crystal structures of compl exes 1-3 are fully described, and their crystallographic data are as f ollows: (1) space group P4 with a = b = 9.083 (2) angstrom, c = 8.092( 2) angstrom, V = 667.5(5) angstrom3, and Z = 2; (2) space group P2(1)/ n with a = 8.694(1) angstrom, b = 8.695(2) angstrom, c = 15.369(2) ang strom, beta = 100.70(1)degrees, V = 1141.6(6) angstrom3, and Z = 2; (3 ) space group P2(1)/c with a = 9.076(2) angstrom, b = 16.813(7) angstr om, c = 16.654(5) angstrom, beta = 102.4(1)degrees, V = 2481(4) angstr om3, and Z = 4.