高价钯参与C—H键卤化反应的还原消除机理研究

Mechanistic Studies on Reductive Elimination in High-oxidation-state Palladium Mediated C—H Bond Halogenation Reactions

运用密度泛函理论方法系统研究了氧化条件下钯催化C—H键卤(氯)化反应的还原消除机理.计算结果表明,C—X(Cl)键的形成过程无Pd(IV)型中间体的参与,还原消除倾向于直接发生在双金属中心的Pd(Ⅲ)-Pd(Ⅲ)型中间体上.作为首例研究Pd(Ⅲ)配合物上还原消除能量需求的研究工作,很好地重现了Ritter等观测的实验现象.理论与实验间良好的相关性不仅证实了该理论方法的可靠性,也为我们未来研究更多钯催化的C—H活化反应提供了良好的理论指导.

Density functional theory （DFT） calculations have been carried out to study the detailed mechanism of Pal-catalyzed reductive elimination in C-H bond halogenation reactions under oxidative conditions. The calculation results show that the C-X （C1） bond formation tends to occur directly on the bimetallic Pd（Ⅲ） intermediate, without the involvement of the Pd（IV） species. As the first theoretical study on the energy profile of reductive elimination on Pd（Ⅲ） intermediates, the current theoretical study shows good agreement with the experimental observations reported by Ritter et aL, which indicates the reliability of the computational methods. The current study also provides insights into further studies on Pd-catalyzed C-H activation reactions.