Pálinkás Noémi, Kollár László, Kégl Tamás
Department of Inorganic Chemistry, University of Pécs, Ifjúság útja 6., H-7624 Hungary.
Dalton Trans. 2017 Nov 21;46(45):15789-15802. doi: 10.1039/c7dt03642f.
The oxidative addition of 4-substituted iodobenzenes on Pd(0) catalysts under CO atmosphere was investigated by means of density functional calculations employing the M06//B97-D3 level of theory. The 18-electron triphenylphosphine-tricarbonyl complex was found to be the global minimum. Several coordinatively unsaturated species are predicted to be present both in N,N-dimethylformamide and toluene solution. In terms of activating iodobenzene, bis(triphenylphosphine)palladium(0) was proved to be the most active. However, due to its lower thermodynamic stability, it is slightly inferior to the Pd-triphenylphosphine-carbonyl complex, which is predicted to react with a free energy of activation of 23.2 kcal mol with respect to the initial resting state tetrakis(triphenylphosphine)palladium(0). The effect of 4-substituents of iodobenzene on reaction energetics is also discussed. The activity of the Pd(0) catalyst was found to be governed by the donor-acceptor strength of the ancillary ligands: the barrier decreases with increasing basicity and decreasing back-donating capability.
采用密度泛函理论的M06//B97-D3水平，通过计算研究了在CO气氛下4-取代碘苯在Pd(0)催化剂上的氧化加成反应。发现18电子的三苯基膦-三羰基配合物是全局最小值。预计在N,N-二甲基甲酰胺和甲苯溶液中均存在几种配位不饱和物种。就活化碘苯而言，双（三苯基膦）钯(0)被证明是最具活性的。然而，由于其较低的热力学稳定性，它略逊于钯-三苯基膦-羰基配合物，预计该配合物相对于初始静止状态的四（三苯基膦）钯(0)，以23.2 kcal mol的活化自由能发生反应。还讨论了碘苯4-取代基对反应能量学的影响。发现Pd(0)催化剂的活性受辅助配体的给体-受体强度控制：随着碱性增加和反馈给电子能力降低，势垒降低。
