M. W. Extine

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.

Tetradecaisopropoxydihydridotetratungsten(IV). Oxidative addition of PrO-H across a tungsten-to-tungsten triple bond

Abstract : The title compound W4(OPr(1)) 14 (H)2 is formed in the reaction between W2(NMe2)6 and Pr(i)OH and has been characterized by a single crystal X-ray study. Formation of this novel tetranuclear complex is accounted for by the following sequence of reactions: (a) alcoholysis, W2 (NMe2)6 + 6PriOH yields W2(OPr(1))6 + 6HNMe2, (b) oxidative addition of Pr(i)O-H across a W=W, W2(OPr(i))6 + Pr(i)O-H yields W2(OPr(i))7(mu-H) W=W distance = 2.446(1) A and (c) association by PriO bridge formation, 2W2(OPr(i))7 (mu-H) yields W4 (OPr(i))14(H)2. (Author)

Detailed structure of bis(.mu.-trimethylsilylmethylidyne)-tetrakis(trimethylsilylmethyl)ditungsten(W-W)

Abstract : The crystal and molecular structures of a compound of composition W2(CSiMe3)2 (CH2SiMe3)4 have been determined. The compound consists of dinuclear molecules which contain bridging alkylidyne groups, CSiMe3, which, along with the tungsten atoms form planar, rhombic rings, W-C-W-C. Two alkyl groups, CH2SiMe3, are attached to each metal atom to form distorted tetrahedra about the metal atoms. There are two crystallographically independent molecules, each residing on a crystallographic inversion center. The two crystallographically independent W-W distances, 2.521(2)A, and 2.549(2)A, are consistent with the presence of W-W single bonds.

Tetracarbonyl ferrate derivatives of (η6-arene)Cr(CO)3: new reagents for carbon–carbon bond formation

The reaction of Na2[Fe(CO)4] and (η6-ClC6H5)Cr(CO)3 in tetrahydrofuran/N-methylpyrrolidinone (THF/NMP) produces Na[(η6-{(CO)4Fe}C6H5)Cr(CO)3], while various (η6-o-LiXC6H4)Cr(CO)3 derivatives react with Fe(CO)5 to produce Li[(η6-o-{(CO)4Fe(CO)}XC6H4)Cr(CO)3] complexes.

The molybdenum-to-molybdenum triple bond. 5. Preparation and structure of dimethyltetrakis(dimethylamido)dimolybdenum

Abstract : The existence of an extensive chemistry centering around the triplybonded Mo-Mo and W-W units is now well established and has recently been reviewed. A firm structural base for interpreting this chemistry has been provided by more than a score of x-ray crystallographic structure determinations. Among these, however, there have been only a few pairs of molybdenum and tungsten compounds with the same or very similar sets of ligands. The comparisons afforded by such pairs are valuable in developing the comparative chemistry of the M-M multiple bonds in the 2nd and 3rd transition series. (Author)

Carbon dioxide exchange reactions involving early transition-metal NN-dimethylcarbamato compounds: reversible insertion of carbon dioxide into transition-metal–nitrogen σ-bonds

Transition-metal NN-dimethylcarbamato compounds ML*n, (where M = Ti, Zr and n= 4; M = Nb, Ta and n= 5), W2L*6 and W(NMe2)3L*3, (L*= O213CNMe2), react with 12CO2 to give MLn, W2L6 and W(NMe2)3L3, where (L = O212CNMe2), with an energy of activation ranging from ca. 54 ± 8kJ mol–1 for ZrL4 to ca. 96kJ mol–1 for W(NMe2)3L3; mixtures of MLn and ML*n scramble CO2 in the absence of an applied CO2 atmosphere.