QUADRUPLY BONDED DIMOLYBDENUM COMPLEXES CONTAINING PAIRS OF BRIDGING DIPHOSPHINE AND ACETATE LIGANDS - SYNTHESIS AND STRUCTURAL CHARACTERIZATION OF TRANS-MO2CL2(OAC)(2)(MU-DPPA)(2) AND ITS TRANSFORMATION TO MO2CL4(MU-DPPA)(2), WHERE DPPA IS N,N-BIS(D

摘要

By reaction of Mo-2(OAc)(4) with (CH3)(3)SiCl and dppa(dppa = Ph2PN(H)PPh2) in THF, two complexes can be prepared. The red complex trans-Mo2Cl2(OAc)(2)(mu-dppa)(2) (i) was obtained in 42% yield while the green complex Mo2Cl4(mu-dppa)(2) (2) was prepared in 31% yield. Complex 2 can also be derived by reacting K4Mo2Cl8 or Mo2Cl4(PPh3)(2)(CH3OH)(2) With dppa in methanal and acetone, respectively. Reaction of 1 with (CH3)(3)SiCl leads to the formation of 2. Their UV-Vis and P-31{H-1} NMR spectra have been recorded and the structures of both 1 and 2 have been determined. Crystal data for 1: space group Pbca, a=16.699(1), b=16.784(1), c=19.728(2) Angstrom, V=5529.3(7) Angstrom(3), Z=4, with final residuals R=0.0606 and R-w=0.0620. The diphosphine ligands are bridged to the metal centers with an eclipsed configuration around the metal-metal bond. The chloride atoms are forced to coordinate to the Mo atoms in the axial positions. Crystal data for 2: space group Ibca, a=16.165(2), b=16.576(2) Angstrom, c=37.024(3) Angstrom, V=9921(2) Angstrom(3), Z=8, with final residuals R=0.0933 and R-w=0.0990. The two dppa ligands are bridged to the metal centers. The interconversions between 1 and 2 are discussed. [References: 20]