中性循环中铱催化甲醇羰基化合成乙酸的理论研究

采用密度泛函理论研究了中性循环中Ir(CO)_3I催化甲醇羰基化制乙酸的反应机理,计算得到了反应路径上各驻点的几何构型与频率,通过能量和振动分析证实了过渡态的真实性.结果表明,Ir(CO)_2I与CH_3I作用后,亲核加成过程出现反应路径中最大能垒(40. 3 kJ/mol),使用能量跨度模型分析了反应过程的动力学信息,确定了反应的能量跨度和决速中间体和决速过渡态分别为IM1和TS12,亲核加成过程为反应的决速步骤,得到了298 K催化剂的转化频率3. 2×10~(-6)s~(-1).

Theoretical study for the neutral catalytic cycles of iridium-catalysed methanol carbonylation

The carbonylation of methanol to acetic acid catalyzed by Ir(CO)3I has been investigated by using the B3LYP level of density functional theory. The geometries for reactants, the transition states and the products are completely optimized. All the transition states are verified by the vibrational analysis and the internal reaction coordinate (IRC) calculations. The results indicate that the largest energy barrier (40.3 kJ/mol) appears in the nucleophilic addition process after Ir(CO)2I molecules are adsorbed on CH3I. Finally, the energetic span model is applied in the cycle reaction to obtain some kinetic information, the determining transition state and the determining intermediate were confirmed to be IM1and TS12, respectively. Finally, the turnover frequency calculated is 3.2×10-6 s-1 at 298K.