Morton Laurel A, Chen Shujian, Qiu He, Xue Zi-Ling
Department of Chemistry, The University of Tennessee, Knoxville, Tennessee 37996, USA.
J Am Chem Soc. 2007 Jun 13;129(23):7277-83. doi: 10.1021/ja067914r. Epub 2007 May 19.
An equilibrium mixture of alkyl alkylidyne W(CH2SiMe3)3(CSiMe3)(PMe3) (1a) and its bis(alkylidene) tautomer W(CH2SiMe3)2(=CHSiMe3)2(PMe3) (1b) has been found to undergo an alpha-hydrogen abstraction reaction in the presence of PMe3 to form alkyl alkylidene alkylidyne W(CH2SiMe3)(=CHSiMe3)(CSiMe3)(PMe3)2 (2). In the presence of PMe3, the formation of 2 follows first-order kinetics, and the observed rate constant was found to be independent of the concentration of PMe3. The activation parameters for the formation of 2 are Delta H = 28.3(1.7) kcal/mol and Delta S = 3(5) eu. In the presence of PMe2Ph, an equilibrium mixture of W(CH2SiMe3)3(CSiMe3)(PMe2Ph) (3a) and its bis(alkylidene) tautomer W(CH2SiMe3)2(=CHSiMe3)2(PMe2Ph) (3b) was similarly converted to W(CH2SiMe3)(=CHSiMe3)(CSiMe3)(PMe2Ph)2 (4). The observed rate of this reaction was also independent of the concentration of PMe2Ph. These observations suggest a pathway in which the tautomeric mixtures 1a,b and 3a,b undergo rate-determining, alpha-hydrogen abstraction, followed by phosphine coordination, resulting in the formation of the alkyl alkylidene alkylidyne complexes 2 and 4.
已发现烷基亚烷基钨 W(CH2SiMe3)3(CSiMe3)(PMe3)（1a）及其双（亚烷基）互变异构体 W(CH2SiMe3)2(=CHSiMe3)2(PMe3)（1b）的平衡混合物在 PMe3 存在下会发生 α-氢抽象反应，形成烷基亚烷基亚烷基钨 W(CH2SiMe3)(=CHSiMe3)(CSiMe3)(PMe3)2（2）。在 PMe3 存在下，2 的形成遵循一级动力学，且观察到的速率常数与 PMe3 的浓度无关。形成 2 的活化参数为 ΔH = 28.3(1.7) kcal/mol 和 ΔS = 3(5) eu。在 PMe2Ph 存在下，W(CH2SiMe3)3(CSiMe3)(PMe2Ph)（3a）及其双（亚烷基）互变异构体 W(CH2SiMe3)2(=CHSiMe3)2(PMe2Ph)（3b）的平衡混合物同样转化为 W(CH2SiMe3)(=CHSiMe3)(CSiMe3)(PMe2Ph)2（4）。该反应的观察速率也与 PMe2Ph 的浓度无关。这些观察结果表明了一种途径，其中互变异构混合物 1a,b 和 3a,b 经历速率决定的 α-氢抽象，随后是膦配位，从而形成烷基亚烷基亚烷基配合物 2 和 4。
