Direct and Autocatalytic Reductive Elimination from Gold Complexes ([(Ph3P)Au(Ar)(CF3)(X)], X = F, Cl, Br, I): The Key Role of Halide Ligands
Direct and Autocatalytic Reductive Elimination from Gold Complexes ([(Ph3P)Au(Ar)(CF3)(X)], X = F, Cl, Br, I): The Key Role of Halide Ligands
复制标题
DOI：
10.1002/chem.201605784
复制
发表时间：
2017-03-23
影响因子：
4.3
通讯作者：
Datta, Ayan
中科院分区：
文献类型：
--
作者：
Bhattacharjee, Rameswar;Nijamudheen, A.;Datta, Ayan
通过计算研究了一系列Au-III配合物[（Ph 3 P）Au（Ar）（CF 3）（X）]（1（X）; Ar=4-Me-C 6 H 4; X=F，Cl，Br，I）中C-芳基-CF 3，C-芳基-X，C-芳基-P和CF 3-X键的还原消除和膦竞争解离的动力学和热力学偏好.动力学上，发现最有利的途径包括从络合物1（X）的初始膦解离，其提供相应的三配位Au-III络合物[Au（Ar）（CF 3）（X）]（2（X））。通过直接（或非催化）机理计算的络合物2（X）的各种还原消除反应的焓垒表明，C-芳基-CF 3键的形成是任何X基团的最有利的命运。当直接消除与通过形成混合价双核Au-III-Au-I中间体进行的自催化机制进行比较时，形成C-芳基-CF 3键的偏好取决于桥接卤素原子的性质，并且遵循F>Cl>Br>I的顺序。同时，对于各种X原子形成C-芳基-X键的选择性遵循相反的趋势。对直接和自催化过程的偏好完全由卤化物配体的性质控制。各种卤化物的预测机制和产品选择性的趋势显示出良好的协议与最近的实验观察。利用分子轨道理论和畸变相互作用模型分析，合理化了各种还原消除途径的选择性。发现Au-I络合物和络合物2X之间的吸引力相互作用降低了C-芳基-X消除的活化势垒，并严格控制产物形成的选择性。
Kinetic and thermodynamic preferences for the reductive elimination of C-aryl-CF3, C-aryl-X, C-aryl-P, and CF3-X bonds and competitive phosphine dissociation from a series of Au-III complexes [(Ph3P)Au(Ar)(CF3)(X)] (1(X); Ar=4-Me-C6H4; X=F, Cl, Br, I) are studied computationally. Kinetically, the most favorable pathways were found to consist of an initial phosphine dissociation from complex 1(X), which furnished the respective three-coordinate Au-III complexes [Au(Ar)(CF3)(X)] (2(X)). The computed enthalpy barriers for various reductive elimination reactions from complex 2(X) by a direct (or uncatalyzed) mechanism showed that C-aryl-CF3 bond formation was the most favorable fate for any X group. When the direct elimination was compared with an autocatalytic mechanism that proceeded through the formation of a mixed-valent binuclear Au-III-Au-I intermediate, the preference for the formation of a C-aryl-CF3 bond is dependent on the nature of the bridging halide atom and follows the order F>Cl>Br>I. Concomitantly, the selectivity for the formation of C-aryl-X bonds for various X atoms follows the opposite trend. The preference for the direct and autocatalytic processes is controlled entirely by the nature of the halide ligand. The predicted mechanisms and product selectivity trends for various halides show excellent agreement with recent experimental observation. The selectivity of various reductive elimination pathways was rationalized by using molecular orbital theory and distortion-interaction model analyses. Attractive interactions between the Au-I complex and complex 2X were found to reduce the activation barrier for C-aryl-X elimination and critically control the selectivity of the product formation.