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采用自然键轨道理论(NBO)分析了吡啶甲酸铑阳离子催化剂([LRh(CO)2]+,L:吡啶甲酸配体)的结构和成键,结合前期研究工作结论,对催化剂从结构上进行了改进,设计了吡啶乙酸铑阳离子催化剂([LCH2-Rh(CO)2]+,LCH2:吡啶乙酸配体),采用从头算HF方法,在LANL2DZ基组下,优化得到了[LCH2-Rh(CO)2]+催化甲醇羰基化制备乙酸反应的决速步骤(CH3I氧化加成)反应物、产物、中间体、过渡态的构型,对反应每一驻点作了零点能(zero-pointenergy,ZPE)校正,计算了反应位垒(130.02kJ/mol),对比[LRh(CO)2]+催化剂,从构型、电荷分布、前线轨道等方面,探讨了吡啶乙酸铑阳离子催化剂具有高活性的本质原因,结果表明[LCH2-Rh(CO)2]+比[LRh(CO)2]+反应活性更高,共轭结构的破坏和六元环的引入使[LCH2-Rh(CO)2]+能够协同CH3I氧化加成,一定程度上降低了反应位垒。
The structures and bonding of rhodium picolinate catalyst ([LRh (CO) 2] +, L: picolinic acid ligand) were analyzed by the theory of natural bond orbital (NBO). Based on the previous work, (LCH2-Rh (CO) 2] + and LCH2: pyridine acetic acid ligand) were designed and synthesized by the ab initio HF method. Under the LANL2DZ basis set, [LCH2-Rh CO 2] + catalyzed methanol carbonylation to the acetic acid reaction rate step (CH3I oxidation addition) reactants, products, intermediates, transition state configuration, the reaction of each stagnation point zero energy (zero-pointenergy , ZPE) were used to calculate the potential barrier (130.02 kJ / mol) and the comparative [LRh (CO) 2] + catalyst. The rhodium pyridinium acetate catalyst was investigated for its activity, configuration, charge distribution and frontier orbital. The results show that [LCH2-Rh (CO) 2] + is more reactive than [LRh (CO) 2] + and the destruction of the conjugated structure and the introduction of six- ] + Can cooperate with the CH3I oxidation addition, to a certain extent, reduce the reaction barrier.