199737-28-5Relevant articles and documents
Dinuclear (d3-d3) Diolate Complexes of Molybdenum and Tungsten. 3.1 Bridging and Chelating Isomers of M2 (NMe2)2(O～～CHMe～～O)2, Where O～～CHMe～～O Is the Dianion of 2,2′-Ethylidenebis(4,6-di- tert-butylphenol). Kinetic versus Thermodynamic Considerations
Chisholm, Malcolm H.,Folting, Kirsten,Streib, William E.,Wu, De-Dong
, p. 50 - 55 (1998)
Hydrocarbon solutions of Mo2(NMe2)6, and 2,2′-ethylidenebis(4,6-di-tert-butylphenol), HO～～CHMe～～OH (2 equiv), react to give a mixture of two isomers, A and B, of formula Mo2(NMe2)2(O～～CHMe～～O) 2. Both A and B are shown to contain the bridging μ-O～～CHMe～～O ligands. They are diastereomers differing with respect to the positioning of the CHMe moiety as a result of ring closure with elimination of HNMe2. Compounds A and B are thermally persistent at 100 °C in the solid state and in toluene, but compound A isomerizes in the presence of pyridine to the thermodynamically favored chelate isomer Mo2(NMe2)2(η 2-O～～CHMe～～O)2, C. Compound C is related to the previously characterized isomer Mo2(NMe2)2(η2-O～～CH 2～～O)2, where the methylene proton that is distal to the Mo-Mo triple bond is replaced by a Me group. Compound B cannot rearrange to this isomer without Mo-O bond dissociation. W2(NMe2)6 and HO～～CHMe～～OH (2 equiv) react to give W2(NMe2)2(η 2-O～～CHMe～～O)2, D, which is an analogue of C. The three molybdenum isomers A-C and tungsten complex D have been structurally characterized by single crystal X-ray studies. The results of this work are discussed in terms of the earlier work involving the related 2,2′-methylenebis(6-tert-butyl-4-methylphenoxides) and reveal that the initial ring closure reaction determines the stereochemistry of the subsequent substitution by the biphenoxide at the dinuclear center. Crystal data: for A·PhMe at - 168 °C, a = 16.585(5) A?, b = 19.480(6) A?, c = 10.960(3) A?, α = 98.39(2)°, β = 103.19(1)°, γ = 91.44(2)°, space group P1?; for B·2PhH at - 168 °C, a = 15.167(3) A?, b = 18.210(3) A?, c = 13.964(3) A?, α = 92.81(1)°, β = 100.40(1)°, γ = 71.16(1)°, space group P1?; for C·1.SEt2O at - 168 °C, a = 16.483(3) A?, b = 16.817(3) A?, c = 14.305(2) A?, α = 106.13-(1)°, β = 108.80(1)°, γ = 71.70(1)°, space group P1?; and for D at - 168 °C, a = 14.638(2) A?, b = 21.188(4) A?, c = 10.273(2) A?, a = 94.80(1)°, β = 95.05(1)°, γ = 100.85(1)°, space group P1?.
