School of Chemistry and Chemical Engineering, Key Laboratory of Mesoscopic Chemistry of Ministry of Education, Institute of Theoretical and Computational Chemistry, Nanjing University, Nanjing, 210093, PR China.
Inorg Chem. 2009 Nov 2;48(21):10257-63. doi: 10.1021/ic9013587.
Density functional theory calculations have been carried out to explore the mechanism of the H(2) activation by the (PNP)Ir(C(6)H(5)) complex. Our calculations show that the reaction is most likely to go though three steps. The first step (also the rate-determining step) involves the proton transfer from the benzylic position of the PNP ligand to the metal center to form an Ir(III) hydride intermediate, accompanied by the dearomatization of the PNP ligand. Second, H(2) is coordinated to the metal of this Ir(III) intermediate to form a molecular hydrogen complex. Finally, the H-H bond is heterolytically cleaved to produce the final trans-dihydride product, in which the benzylic carbon is protonated, and the PNP ligand is rearomatized. Thus, the H(2) activation by the Ir(I) complex actually involves an Ir(III) hydride complex as a key intermediate. The Ir center and the PNP ligand cooperate in a synergistic manner in the H(2) activation process. The above molecular mechanism could provide reasonable explanations for known experimental facts.
已运用密度泛函理论计算来探究（PNP）Ir（C6H5）复合物活化 H2 的反应机理。我们的计算表明，该反应最有可能经历三个步骤。第一步（也是速率决定步骤）涉及 PNP 配体的苄位质子向金属中心转移，形成 Ir（III）氢化物中间体，同时 PNP 配体去芳构化。第二步，H2 与该 Ir（III）中间体的金属配位，形成分子氢络合物。最后，H-H 键异裂生成最终的反式二氢化物产物，其中苄基碳质子化，PNP 配体再芳构化。因此，Ir（I）配合物活化 H2 实际上涉及 Ir（III）氢化物络合物作为关键中间体。Ir 中心和 PNP 配体在 H2 活化过程中协同作用。上述分子机理可以为已知的实验事实提供合理的解释。
