73133-22-9Relevant academic research and scientific papers
Reactions of ML4Cl2 (M = Mo, W; L = PMe3, PMePh2) with epoxides, episulfides, CO2, heterocumulenes, and other substrates: A comparative study of oxidative addition by oxygen atom, sulfur atom, or nitrene group transfer
Hall, Keith A.,Mayer, James M.
, p. 10402 - 10411 (2007/10/02)
A comparative survey of the reactivity of the divalent molybdenum and tungsten chloro-phosphine complexes ML4Cl2 (M = Mo, W; L = PMe3, PMePh2) toward oxidation by a variety of oxygen atom, sulfur atom, and nitrene donors is presented. In general, reactions result in net two-electron oxidation of the metal center, producing metal oxo, sulfido, and imido complexes. The reactions can also be described as oxidative addition reactions, in many cases oxidative addition of C=X double bonds. Reactions are apparently thermodynamically driven by the propensity of Mo and W to form strong multiple bonds with oxygen, sulfur, and nitrogen. ML4Cl2 compounds react with ethylene oxide and ethylene sulfide to produce oxo and sulfido tris(phosphine) species, M(E)L3Cl2 (E = O, S), in equilibrium with oxo and sulfido ethylene species M(E)(CH2=CH2)L2Cl2. Isocyanates (RN=C=O; R = tBu, p-tolyl) and tBuN=C=NtBu react to form imido tris(phosphine) and imido carbonyl or imido isonitrile complexes, respectively. Phosphine sulfides are desulfurized forming sulfido complexes, but phosphine oxides are unreactive. The π-acids formed in these reactions - for instance, CO from cleavage of RNCO - bind more strongly to the tungsten(IV) versus the molybdenum(IV) oxo, sulfido, and imido products. Similarly, the equilibria for π-acid coordination are more favorable when the ligand is PMePh2 than when L = PMe3. For all of the complexes, reactions are slowed by free phosphine, consistent with a mechanism involving an initial dissociation of a phosphine ligand followed by trapping of the coordinatively unsaturated species by the oxidizing substrate. Ligand loss from ML4Cl2 is rapid for L = PMePh2 at ambient temperatures but slower for L = PMe3, with half-lives for PMe3 loss of 18 min at 24°C for Mo(PMe3)4Cl2 and 6 min at 69°C for W(PMe3)4Cl2. For the molybdenum complexes MoL4Cl2 (L = PMe3, PMePh2), dimerization to the known Mo(II) quadruply bound species Mo2L4Cl4 is competitive with oxidation at the metal center. In reactions involving stronger oxidants (SO2, DMSO, and N2O), the formation of trivalent species ML3Cl3 is often observed, indicating that chlorine atom transfer processes also occur.
Preparation of W2Cl84- and several of its derivatives
Schrock, Richard R.,Sturgeoff, Lynda G.,Sharp, Paul R.
, p. 2801 - 2806 (2008/10/08)
The sodium amalgam reduction of WCl4 in tetrahydrofuran in the presence of a tertiary phosphine (L = PMe3, PBu3, PMe2Ph, PMePh2) produces a family of compounds of the type W2Cl4L4, which contain a tungsten-tungsten quadruple bond. W2Cl4(dmpe)2 and W2Cl4(dppe)2 must be prepared by the reaction between W2Cl4(PBu3)4 and dmpe or dppe. In the absence of phosphine, WCl4 can be reduced to W2Cl6(THF)4. W2Cl6(THF)4 reacts with phosphine to produce W2Cl6L4, and W2Cl6L4 can be reduced cleanly to W2Cl4L4. In the absence of phosphine W2Cl6(THF)4 can be reduced to deep blue Na4(THF)xW2Cl8. Several other derivatives such as Na4(TMEDA)4W2Cl8 have also been prepared. All derivatives that contain the W2Cl84- ion decompose within a few minutes at 25°C in solvents in which they dissolve. Na4(THF)xW2Cl8 reacts rapidly with phosphine to produce W2Cl4L4, with 6-methyl-2-hydroxypyridine in the presence of triethylamine to produce W2(mhp)4, and with pivalic acid in the presence of triethylamine to produce W2(O2CCMe3)4. We have shown that complexes of the type W2Cl4L4 can be oxidized readily to monocations. An attempt to prepare W2(O2CCH3)4 from W2Cl4(PBu3)4 and acetic acid also led to oxidation of the metal to give W3O3Cl5(O2CCH3)(PBu 3)3.
