钯的烷基双膦配合物催化芳基卤化物与硫醇偶联的静止状态和基本步骤,Journal of the American Chemical Society

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钯的烷基双膦配合物催化芳基卤化物与硫醇偶联的静止状态和基本步骤
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2009-06-10 , DOI: 10.1021/ja901793w
Elsa Alvaro ₁ , John F Hartwig

Affiliation

报道了烷基双膦配体 CyPF-(t)Bu（1-二环己基膦基-2-二叔丁基膦基乙基二茂铁）的钯配合物催化芳基卤化物与硫醇偶联的详细机理研究。已经研究了构成催化循环的基本步骤，即氧化加成、金属转移和还原消除，并报告了它们的相对速率。催化过程的每个步骤都在远低于由钯前体和 CyPF-(t)Bu 组合催化的反应所需的温度下进行。为了解释催化反应和化学计量反应之间的这些速率差异，进行了研究以确定由 Pd(OAc)(2) 和 CyPF-(t)Bu 组合催化的反应的催化剂的静止状态，Pd(dba)(2) 和 CyPF-(t)Bu 的组合，或可能的中间体 Pd(CyPF-(t)Bu)(Ar)(Br)。这些数据表明，在每种情况下，主要的钯配合物都处于催化循环之外。由 Pd(OAc)(2) 和 CyPF-(t)Bu 催化的反应的静止状态是钯双硫醇盐络合物 [Pd(CyPF-(t)Bu)(SR)(2)] (R = 烷基或芳基）。由 Pd(2)(dba)(3) 和 CyPF-(t)Bu 催化的反应的静止状态是双核复合物 [Pd(CyPF-(t)Bu)](2)(mu(2),eta( 2)-dba) (9). [Pd(CyPF-(t)Bu)(p-tolyl)(Br)] (3a) 催化的芳香族和脂肪族硫醇反应的静止状态是氢化钯硫醇配合物 [Pd(CyPF-(t)Bu) (H)(SR)]（R=烷基和芳基）。所有这些钯物种都是独立制备的，并详细研究了它们进入催化循环的机制。由钯和 CyPF-(t)Bu 催化的反应的这些特征已与由烷基双膦 DiPPF 和 Pd(OAc)(2) 或 Pd(dba)(2) 催化的反应进行了比较。我们的数据表明这些反应的静止状态彼此相似，我们关于钯和 CyPF-(t)Bu 催化反应的机理结论可以外推到由其他富电子双膦配合物催化的反应。

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Resting State and Elementary Steps of the Coupling of Aryl Halides with Thiols Catalyzed by Alkylbisphosphine Complexes of Palladium

Detailed mechanistic studies on the coupling of aryl halides with thiols catalyzed by palladium complexes of the alkylbisphosphine ligand CyPF-(t)Bu (1-dicyclohexylphosphino-2-di-tert-butylphosphinoethylferrocene) are reported. The elementary steps that constitute the catalytic cycle, i.e. oxidative addition, transmetalation and reductive elimination, have been studied, and their relative rates are reported. Each of the steps of the catalytic process occurs at temperatures that are much lower than those required for the reactions catalyzed by a combination of palladium precursors and CyPF-(t)Bu. To explain these differences in rates between the catalytic and stoichiometric reactions, studies were conducted to identify the resting state of the catalyst of the reactions catalyzed by a combination of Pd(OAc)(2) and CyPF-(t)Bu, a combination of Pd(dba)(2) and CyPF-(t)Bu, or the likely intermediate Pd(CyPF-(t)Bu)(Ar)(Br). These data show that the major palladium complex in each case lies off of the catalytic cycle. The resting state of the reactions catalyzed by Pd(OAc)(2) and CyPF-(t)Bu was the palladium bis-thiolate complex [Pd(CyPF-(t)Bu)(SR)(2)] (R = alkyl or aryl). The resting state in reactions catalyzed by Pd(2)(dba)(3) and CyPF-(t)Bu was the binuclear complex [Pd(CyPF-(t)Bu)](2)(mu(2),eta(2)-dba) (9). The resting states of reactions of both aromatic and aliphatic thiols catalyzed by [Pd(CyPF-(t)Bu)(p-tolyl)(Br)] (3a) were the hydridopalladium thiolate complexes [Pd(CyPF-(t)Bu)(H)(SR)] (R= alkyl and aryl). All these palladium species have been prepared independently, and the mechanisms by which they enter the catalytic cycle have been examined in detail. These features of the reaction catalyzed by palladium and CyPF-(t)Bu have been compared with those of reactions catalyzed by the alkylbisphosphine DiPPF and Pd(OAc)(2) or Pd(dba)(2). Our data indicate that the resting states of these reactions are similar to each other and that our mechanistic conclusions about reactions catalyzed by palladium and CyPF-(t)Bu can be extrapolated to reactions catalyzed by complexes of other electron-rich bisphosphines.

更新日期：2009-06-10

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