59752-93-1Relevant 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.
Complexes containing unbridged homonuclear or heteronuclear quadruple bonds. Crystal and molecular structures of MoWCl4(PMePh2)4, MoWCl4(PMe3)4, and Cl2(PMe3)2MoWCl2(PMePh 2)2
Luck, Rudy L.,Morris, Robert H.,Sawyer, Jeffery F.
, p. 2422 - 2429 (2008/10/08)
The reactions of Mo(η6-PhPMePh)(PMePh2)3 and Mo(η6-PhPMe2)(PMe2Ph)3 with MoCl4(THF)2 yield the homonuclear unbridged quadruply bonded complexes Mo2Cl4(PR3)4 (PR3 = PMePh2 (1), PMe2Ph (2)). Complex 1 readily undergoes phosphine substitution with PMe3 to yield Mo2Cl4(PMe3)4 (3). The reactions of Mo(η6-PhPMe2)(PMe2Ph)3 and Mo(η6-PhPMePh)(PMePh2)3 with WCl4(PPh3)2 yield the complexes MoWCl4(PR3)4 (PR3 = PMe2Ph (4), PMePh2 (5)), which are among the first to contain an unbridged quadruple bond between two different elements. Complex 5 undergoes phosphine substitution reactions with PMe3 to give sequentially Cl2(PMe3)2MoWCl2(PMePh 2)2 (6) and then MoWCl4(PMe3)4 (7). Complex 4 can also be synthesized by reacting 5 with PMe2Ph. The 31P and 1H NMR spectra, electronic and visible spectra, and cyclic voltammograms of these complexes are interpreted, and the crystal and molecular structures of 5-7 are reported. Compounds 5 and 7 were found to have disordered arrangements of the metal atoms; compound 6 with the different phosphine ligands on the metal atoms is, however, ordered with a Mo4-W bond length of 2.207 (1) A?. In 6 and 7 the molecules have crystallographic 2-fold symmetry. In all three structures the ligand arrangement over the metal-metal bond defines an eclipsed geometry with chlorine next to phosphine across the bond in a pseudo-D2d arrangement. The metal-metal distances in 5 and 7 are 2.208 (4) (average) and 2.2092 (7) A?, respectively. These values are close to distances expected on the basis of homonuclear M4-M bonds, and therefore there is no extra shortening of these bonds due to electronegativity differences. Crystal data: 5, monoclinic, space group P21/a, a = 21.511 (4) A?, b = 12.176 (6) A?, c = 40.863 (8) A?, β = 92.65(2)°, V = 10692 A?3, Dcalcd = 1.52 g cm-3 for Z = 8, R = 0.0957 for 3554 observed (I > 3σ(I)) reflections; 6, monoclinic, space group I2/a, a = 16.817 (4) A?, b = 11.925 (3) A?, c = 19.685 (5) A?, β = 103.87 (2)°, V = 3832.4 A?3, Dcalcd = 1.69 g cm-3 for Z = 4, R = 0.0364 for 2203 observed reflections; 7, monoclinic, space group I2/a, a = 17.312 (4) A?, b = 9.193 (1) A?, c = 19.085 (3) A?, β = 119.69 (2)°, V = 2638.9 A?3, Dcalcd = 1.57 g cm-3 for Z = 4, R = 0.0312 for 2084 observed reflections.
