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  • 1
    ISSN: 1572-8862
    Keywords: Tungsten ; triple bond ; alkoxide ; amide ; β-diketonate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The reactions between 1,2-W2 R 2(NMe2)4 (R=Et and Ph) and 1,2-W2 R 2(OPr i )4 (R=CH2Ph and Bu t ) and Bu t -CHCOCH2COBu t (Bu t -acacH) (4 equiv)in pentane or hexane give, respectively, W2 R 2NMe2)2 (Bu t -acac)2 and W2 R 2(OPr i )2 (Bu t -acac)2 that are remarkably thermally and photochemically robust with respect to further reaction and reductive elimination to give the targeted compounds W2(Bu t -acac)4. The new compounds have been characterized by elemental analysis, infrared, and1H NMR spectroscopy and forR = Et and CH2Ph by single crystal X-ray studies. In each compound there are four coordinate W atoms united by unbridged W-W triple bonds. Crystal data for W2Et2(NMe2)2 (Bu t -acac)2 at −165°C:a=17.115(2) Å,b=10.542(1) Å,c = 19.786(3) Å.β = 98.55(1)°,Z = 4, and space group C2/c; for W2(CH2Ph)2 (OPr i )2 (Bu t -acac)2 at −157°C:a=23.547(5) Å,b = 10.784(2)Å,c = 21.105(5) Å,β = 127.20(1)°,Z = 4, and space group C2/c.
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  • 2
    ISSN: 1572-8862
    Keywords: Alkoxide ; tungsten ; cluster ; carbide ; hydride
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract A minor product in the reaction between W2(NMe2)6 and neopentanol in hydrocarbon solvents has been isolated and characterized by elemental analysis,1H and13C NMR spectroscopy and a single crystal X-ray study. At −174°C,a=11.669(1) Å,b=25.801(5) Å,c=24.345(4) Å, β=100.91(1)°,Z=4,d calcd=1.60 g cm−3, and space group P21/c. The compound is formulated as W4(μ4-C)(NMe)(OCH2Bu t )11 (H). There is a W4-butterfly and the carbido group is cradled between the wing-tip and back-bone W atoms with W-C=1.90–1.96 and 2.20–2.26 Å, respectively. The five W-W bonding distances span a narrow range 2.74–2.84 Å. The structure of this molecule resembles that previously reported for W4(μ4-C)(NMe)(OPr i )12 where one OPr i ligand bonded to a backbone W atom is replaced by a hydride ligand. The hydride was not located crystallographically but is implicated by (i)a void at one W atom, (ii) itstrans-influence as determined by the W-O bond distance of the group trans to the void, and (iii) electron counting which requires the presence of a W4(μ4-C)14+ rather than a W4(μ4-C)13+ moiety in order to account for the observed diamagnetism. The present finding is compared with the previous preparations and characterizations of W4(μ4-C)14+ alkoxide supported clusters.
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  • 3
    ISSN: 1572-8862
    Keywords: Tungsten ; chloro ; phosphine ; tetranuclear cluster
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract From the reaction between W2Cl6(PEt3)2 and H2O in tetrahydrofuran the dark green crystalline compound [Et3PH][W4O3Cl7(PEt3)3] was obtained and characterized by X-ray crystallography. At −155° the cell dimensions werea=b=c=20.392(3) Å,Z=8,d calcd=2.36 g cm−3 in the space group I23. The compound is a triethylphosphonium salt of the [W4O3Cl7(PEt3)3]− anion. The latter contains a tetrahedron of tungsten atoms with W−W=2.61 Å (ave) and may be viewed as a W3(μ-Cl)3Cl3(PEt3)3 cluster capped by ad 0-[WO3Cl]− unit and this has proved useful in examining the bonding within the cluster by use of the M.O. calculational method of Fenske and Hall. The cluster anion has crystallographically imposed C3v symmetry. Theoxo-groups bridge the tungsten atoms in a notably asymmetric manner W−O=1.87(2) Å and 2.04(2) Å with the shorter distances being involved with the capping [WO3Cl]− unit. The W−P bonds lie in the W3(μ3-Cl)3 plane and the three terminal W−Cl bonds are trans to theoxo-bridges.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of cluster science 6 (1995), S. 135-145 
    ISSN: 1572-8862
    Keywords: Tungsten ; octanuclear cluster ; oxo ; alkoxide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract From the reaction between W4(p-tolyl)2(O-i-Pr)10 and H2, in hydrocarbon solvents, the compound [W4(O)2(O-i-Pr)8]2, 1, has been isolated in ca. 25% yield. Formation of 1 is traced to the decomposition of a compound of formula [W4O-i-Pr)10] n , which has been characterized only by1H NMR spectroscopy. The latter is formed by the stepwise hydrogenolysis of W4(p-tolyl)2(O-i-Pr)10 + H2 → W4(H)(p-tolyl)(O-i-Pr)10 + toluene; W4(H)(p-tolyl)(O-i-Pr)10 → [W4(O-i-Pr)10] n + toluene. In the presence of a small amount of H2O2 the previously characterized compound W4(O)(O-i-Pr)10, 2, is formed. The structure of 1 consists of two pseudo W4 tetrahedra linked through the agency of a pair of alkoxide bridges that bind two tungsten atoms that in turn cap triangles, W3(O)2(O-i-Pr)7, of tungsten atoms. At −176°C the cell dimensions werea=12.600(3),b=14.722(3),c=12.585(2),β=119.77(1),Z=1, andd calcd = 2.240 g cm−3 in the space group P1¯. The W-W distances within these triangles are ca. 2.9 Å whereas the capping W-W atom distances are ca. 2.5 Å. The1H NMR spectrum of 1 in benzene-d6 is consistent with the maintenance of the solid-state structure in solution.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1572-8862
    Keywords: Molybedum ; alkoxide ; oxo ; cluster
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract From the reaction between Mo2(OCH2But)6 and water (1/2 equiv) in toluene solution in the presence of pyridine the oxo-alkoxide tetranuclear cluster Mo4O(OCH2But)10(py) has been isolated as a dark crystalline compound. Crystal data at −121°C:a=24.762(12) Å,b=24.799(9) Å,c=23.021(9) Å,Z=8,d caled=1.27 g cm−3 in space group 14/m. The compound contains a Mo4 butterfly with a hinge angle of 137° between the two Mo3 triangles. The molecule has a crystallographically-imposed mirror plane of symmetry that contains the wing-tip Mo atoms. One wing-tip Mo atom is in an octahedral environment being bonded to two terminal and two-bridging OR ligands, and one pyridine ligand that is trans to a μ3-oxo bridge. The other Mo atoms are each coordinated to only four oxygen atoms. The backbone Mo atoms have one terminal and two bridging OR ligands and form one bond each to the μ3-oxo group. The other wing-tip Mo atom is coordinated to two terminal and two bridging OR groups. The five Mo-Mo distances span the range 2.43–2.59 Å. The1H and13C{1H} NMR spectra in benzene-d6 are consistent with the presence of this structure in solution. The present results are compared to earlier findings for 12-electron alkoxide clusters of Mo and W.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Transition metal chemistry 3 (1978), S. 321-333 
    ISSN: 1572-901X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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