MULTINUCLEAR METAL-CARBONYL ALKOXIDE AND ARYLOXIDE DERIVATIVES AS MODELS FOR METAL-CARBONYLS ADSORBED ON METAL-OXIDE SUPPORTS

The synthesis and characterization of two tungsten carbonyl dimers containing bridging alkoxide or aryloxide ligands are described. The crystal and molecular structures of [PPN]2[W2(CO)8(OCH2CF3)2], 1, and [Et4N]3[W2(CO)6(OPh)3].CH2CN, 2, are reported and compared with the structures of tetranuclear tungsten derivatives previously described. The dimer 1 crystalizes in the triclinic space group P 1BAR with unit cell parameters a = 13.460(11) angstrom, b = 12.318(5) angstrom, c = 13.842(10) angstrom, alpha = 82.73(5) degrees, beta = 59.11(5) degrees, gamma = 80.09(5) degrees, V = 1938(2) angstrom 3, and Z = 1. The complex 2 crystalizes in the monoclinic space group P2(1)/n with unit cell parameters a = 11.954(2) angstrom, b = 19.359(4) angstrom, c = 26.462(5) angstrom, beta = 102.50(16) degrees, V = 5979(2) angstrom 3, Z = 4. Molecular modeling software was utilized to construct a tetranuclear derivative from 1 similar to the structurally characterized [W(CO)3OH]4(-4) tetramer. The two tetramers were found to possess similar molecular parameters. This supports the contention that dimers of type 1 are the precursors of the tetramers. Comparisons of the tungsten alkoxides and aryloxides with the behavior of W(CO)6 on gamma-alumina are provided.