吡啶甲酸铑阳离子催化甲醇羰基化反应IRC解析及催化剂结构与性能的理论计算

Theoretical study for geometries,IRC and catalytic performance of methanol carbonylation over pyridinecarbonylic acid rhodium cation

分别采用从头算HF方法和密度泛函(DFT)B3LYP方法,在LANL2DZ基组下,应用内禀反应坐标(IRC)理论分析吡啶甲酸铑阳离子催化甲醇羰基化决速步骤反应沿最小能量途径(MEP)上相互作用分子间化学键的变化,对比[Rh(CO2)I2)]-催化剂,从催化剂结构、分子轨道分布等方面,探讨吡啶甲酸铑阳离子催化剂具有较高活性的本质原因;同时也从分子轨道和构型分析上总结吡啶甲酸铑阳离子催化剂的缺陷,刚性的五元环结构和离域π键的存在不利于协同决速步骤反应的结构挠变,并提出优化催化剂构型的有效途径.

Density functional theory（DFT） and ab initio Hartree-Fock（HF） had been performed on rate-determining step of methanol carbonylation over pyridine carbonylic acid rhodium cation（＋,where M=pyridine carbonylic acid ligand）.All structural geometries of reactant,intermediates,transition states and product,respectively,were optimized at in the HF/LANL2DZ and B3LYP/ LANL2DZ level.Next,changes of bond lengths of interacting molecules were analyzed along the minimum energy paths（MEP） with the intrinsic reaction coordinate（IRC） theory.Finally,by analyzing molecule obit distributing and geometry,the limitation of＋ hed been reached.The results indicated that＋ had been better catalytic active than[Rh（CO）2I2）]-.But the formation and characteristic of the rigid 5-membered ring and delocalization π bond between C2 and C11 was a disadvantage for it.