有机铼化合物互变异构反应机理的理论研究

采用B3LYP方法研究了有机铼化合物(Me)2(NHR3)Re(=CHR1)(=NR2)与(Me)2(NHR3)Re(≡CR1)(NHR2)之间的异构化反应机理(R1, R2, R3=H, Me, But). 确定了相应的过渡态结构和反应活化能.结果表明, 分子内氢转移过程所需活化能很大;两个反应物分子间的氢转移过程需要的活化能也较大;分子与水间氢转移需要的活化能较小, 分子与HCl间氢转移需要的活化能最小. 结果还表明, 对所研究的四种途径, 取代基对反应活化能的影响相同, R1=Me或But, R2=H, R3=But时反应活化能最小, 并且取代基对反应活化能的影响存在加和性.

A Theoretical Study on Isomerization Mechanism Between Organorhenium Alkylidene and Alkylidyne Complexes

A theoretical study on the isomerization mechanism between organorhenium alkylidene and alkylidyne complexes(Me)2(NHR3)Re(=CHR1)(=NR2) and(Me)2(NHR3)Re(≡CR1)(NHR2), where R1,R2, R3=H,Me,But, were carried out with the density functional theory B3LYP method. The optimal structures of the transition states were located and the activation energies were calculated. The calculation results indicate that the intramolecular hydrogen transfer process is kinetically unfavorable because the high activation energies exists whatever the substituent is. The intermolecular hydrogen transfer process between two alkylidene complexes is less favorable either. The hydrogen transfer process between the alkylidene complex and the water molecule is favorable. The most favorable process is the hydrogen transfer process between the alkylidene complex and the chlorine hydride molecule where the chlorine hydride molecule acts as a bridge or a catalyst. The calculation results suggest that the effects of substituents on the reaction barriers of hydrogen transfer processes are almost the same for all the four processes considered in this work. For each process the most preferable substituents are the methyl or t-butyl group for R1, the hydrogen atom for R2, and t-butyl group for R3. The calculation results also show that the additivity exists for the effects of substituents on the barriers of the α-hydrogen transfer reactions.