D. A. Haitko

The tungsten-tungsten triple bond. 8. Dinuclear alkoxides of tungsten(III) and structural characterization of hexaisopropoxybis(pyridine)ditungsten, the first compound with four-coordinated tungsten atoms united by a triple bond

Abstract : The great majority of compounds containing metal-metal triple bonds of the x3mmx3 type where X is a monodentate ligand (including some where the ligand atmos are not all the same) have perfectly, or almost perfectly, staggered ethane-like rotational conformations. The great majority of compounds containing metal-metal quadruple bonds are of the type X4MMX4 ( again including those where more than one type of ligand is present) and have essentially eclipsed rotational conformations. The relatively few exceptions to each of these generalizations are of interest because they provide further insight into the nature of metal-metal multiple bonds.

Molybdenum-molybdenum triple bond. 9. Bis(1,3-di-p-tolyltriazenido)bis(dimethylamido)dimethyldimolybdenum

Abstract : 1,2-Mo2Me2(NMe2)4 reacts in hydrocarbon solvents with 1,3-di-p-tolyl-triazine, C7H8NNNHC7H8, to give the title compound as a red crystalline solid. An X-ray study shows that in the solid state, the molecule has a crystallographically imposed C2 axis of symmetry. The Mo=Mo bond, 2.174(1)angstroms, is bridged by a cis-pair of triazenido ligands which afford sufficient flexibility to allow a non-eclipsed geometry. Each molybdenum atom is coordinated to three nitrogen atoms and one carbon atom which roughly lie in a plane. Pertinent bond distances are Mo-C (methyl) = 2.193(4) angstroms, Mo-N (dimethylamido) = 1.948(3) angstroms, Mo-N (triazinido) = 2.157(3) and 2.283(3) angstroms, with the longer distance associated with the Mo-N bond which is trans to the Mo-CH3 bond. These observations are compared with other findings in dimolybdenum and ditungsten chemistry (M=M). Crystal data for Mo2Me2(NMe2)2-(C7H8N3C7H8)2 are a = 21.608(5) angstroms, b = 9.440(2) angstroms, c = 24.076(6) angstroms, = 135.49(1), V = 3442.5(1) angstroms(cubed), Z = 4, d sub calcd = 1.464 g cc and space group C2/c. (Author)