【摘要】 采用密度泛函理论方法,模拟了Rh(PPh3)3Cl催化的C—H键活化/C—C键偶联反应.将反应机理分为C—H键活化、迁移插入和还原消除3个过程进行讨论.计算结果表明,势能面的最高点为迁移插入的过渡态,相对于初始原料的自由能为108.3 kJ/mol.为了探索简化计算模型对模拟反应机理的影响,使用2种模型催化剂Rh(PMe3)3Cl和Rh(PH3)3Cl表征相同的反应过程,结果表明配体简化模型不合理,主要是因为PPh3配体的空间效应和熵效应非常明显.更多还原

【Abstract】 Density functional theory method was employed to simulate a Rh( PPh 3) 3 Cl catalyzed C—H activation / C—C cross-coupling reaction,in which three typical processes,namely,C—H activation,migratory insertion and reductive elimination,were characterized. The obtained results show that the rate-determining step is migratory insertion with the free-energy barrier of 108. 3 kJ / mol. In order to test the validation of truncated models,two small catalysts Rh( PMe 3) 3 Cl and Rh( PH 3) 3 Cl were also used to study the same coupling reaction. Our calculations suggested that truncated models led to misunderstanding of reaction mechanism and freeenergy changes,especially for migratory insertion process,since the steric effect and entropic contribution play a great role on these types of reactions.更多还原