杂双核Rh-M (M＝Cr, Mo, W)物种中羰基插入 RhI—C键的密度泛函研究

采用密度泛函方法研究了配体和协同金属对杂双核Rh-M金属配合物中羰基插入反应的影响. 计算结果表明所有羰基插入过渡态均为后过渡态, 其结构较接近于产物. 羰基插入Rh—Cvinyl键要比插入Rh—Cethyl键容易. 对于CO插入Rh—Cethyl键, CO配体在热力学上有利于该反应, 而在动力学上不利于此反应. 羰基插入Rh—Cvinyl键过程中, CO配体则在动力学和热力学上均促进该反应. 不管羰基插入Rh—Cethyl键还是Rh—Cvinyl键, 相同配体不同协同金属时, 反应顺序如下: Cr＜Mo＜W. 能量分解分析表明, 羰基插入Rh—Cvinyl键的活化能低于羰基插入Rh—Cethyl键的主要原因为过渡态中乙烯基片段与羰基片段的相互作用能比乙基片段与羰基片段的相互作用能强.

Density Functional Theory Study on Carbonyl Insertion into RhI-C Bond in Heterobimetallic Rh-M (M=Cr, Mo, W) Species

The influence of ligand and cooperative metal on carbonyl insertion in heterobimetallic Rh-M species was investigated at the B3LYP level of density functional theory. The computational results indicate that all of the transition states of the carbonyl insertion occur lately on the potential energy surface. The carbonyl insertion into the Rh—Cvinyl bond is easier than that into the Rh—Cethyl bond. The CO ligand promotes the carbonyl insertion into the Rh—Cethyl bond thermodynamically, while it inhibits this reaction kinetically. The CO ligand is in favor of the carbonyl insertion into the Rh—Cvinyl bond both thermodynamically and kinetically. The reactivity of the various cooperative metals with the same ligand for the carbonyl insertion into the Rh—Cethyl and Rh—Cvinyl bonds has following order: Cr＜Mo＜W. The energy decomposition analysis indicates that the lower activation energy of the carbonyl insertion into the Rh—Cvinyl bond than that of the carbonyl insertion into the Rh—Cethyl bond should be caused by the stronger interaction energy between carbonyl and vinyl fragments in transition states of the carbonyl insertion into the Rh—Cvinyl bond than that of the carbonyl insertion into the Rh—Cethyl bond.