含有铱、釕金属有机化合物参与反应的机理理论研究

【作者】 曹向辉；

【导师】 毕思玮；

【作者基本信息】 曲阜师范大学 ， 无机化学， 2010， 硕士

【摘要】 在本文中,我们用密度泛函理论(DFT)中的B3LYP方法,研究了如下两个方面的问题,主要目的是研究相关金属有机化合物参与的反应的反应机理及反应中各物质的分子结构及成键特征。首先在实验事实的基础上,为了深入探讨酮的直接氢化反应机理,我们借助密度泛函理论的B3LYP方法,用模型化合物IrH3[(Me2PC2H4)2NH],研究了IrH3[(iPr2PC2H4)2NH]催化下的具有代表性的3-戊酮与与H2直接氢化反应的机理,展示了在整个催化循环过程中,过渡金属配合物的几何构型转变,反应的催化剂是模型化了的铱的化合物IrH3[(Me2PC2H4)2NH],主要是研究了反应中提到的各物质的键能、键长,反应性能及与反应性能有关的热力学、动力学参数。另外还比较了五配位含铱化合物Int4与H2配位又重新生成原始催化剂的过程中的两种路径,一种路径是经历一个三元环的过渡态,第二种路径是经历四元环的过渡态,理论预测,催化剂的再生(Int4与H2反应)经历一个四元环过渡态而不是经历一个三元环过渡态。另外还比较了转移氢化和直接氢化两种过程的不同,发现转移氢化在动力学上更有利,直接氢化决速步骤需要克服的能垒高,比转移氢化更难进行,需要实验条件提供一定的压力才能顺利进行。文中还运用过渡金属化合物的分子轨道理论研究了在整个催化循环中,催化剂由八面体到Y-型又到八面体的几何构型改变。其次应用同样的方法,在密度泛函理论的方法的指导下我们利用模型化合物μ-苯醌二钌化合物{CpRu(μ-H)}2(μ-η2:η2-C6H4O2),研究了实验物质{Cp*Ru(μ-H)}2(μ-η2:η2-C6H3RO2) (R=HorR=Me,Cp*=η5-C5Me5)与乙炔分别在非质子溶剂和质子溶剂中的反应机理。计算结果表明质子溶剂(甲醇)主要是对乙炔与金属中心配位的过程产生影响,另外还讨论了在质子溶剂和非质子溶剂中的两种反应机理,通过分析可知由于在甲醇和苯醌之间形成了氢键,使得从Ru金属中心到苯醌的π*轨道的电子转移被加强。为了探究乙炔为何更容易在甲醇溶剂中配位,我们又做了能量分解分析(EDA),双核多聚氢化物中包含的氢键导致了金属Ru的酸性增加是反应速率在质子溶剂中加快的原因。更多还原

【Abstract】 Density functional theory (DFT) calculations at the B3LYP level of theory are carried out to study and analyze the following two projects. Our major purpose is to investigate the molecular structures, bonding, and mechanisms of the reactions in the three different projects in which most of the species are organometallic compounds.First,with the aid of the density functional theory calculations, the detailed catalytic mechanisms on pressure hydrogenation of ketones are explored by employing the representative reaction of 3-pentanone and hydrogen catalyzed by the model complex IrH3[(Me2PC2H4)2NH], derived from the initial catalytic complex IrH3[(’Pr2PC2H4)2NH]. The geometrical transformation involved in the catalytic cycle is also clarified. We also compare the two paths in the process of pentacoordinate iridium complex Int4 coordinating with hydrogen to regenerate the original catalyst. One undergoes a three-membered ring transition state, the other possesses a four-membered ring transition state. As the four-membered ring of the ring strain is less than three-membered ring, the second path possesses a lower reaction energy barrier, reaction will according to the second path. In addition, differences between transfer hydrogenation and pressure hydrogenation are also elucidated, finding that transfer hydrogenation is more favorable since the reaction energy barrier of pressure hydrogenation is higher than the other one. Then experimental conditions required to provide a certain degree of pressure. The geometrical transformation from an octahedron to a Y-type involved in the catalytic cycle is also elucidated in terms of molecular theory of transition metal complexes.Then,by the aid of density functional theory (DFT) calculations we studied the reaction mechanisms of a modelμ-benzoquinone diruthenium complex{CpRu(μ-H)}2(μ-η2:η2-C6H4O2), derived from the experimental compound{Cp*Ru(μ-H)}2(μ-η:η-C6H3RO2) (R=H or R=Me, Cp*=η5-C5Me5), with acetylene both in aprotic and protic solvents. Results of calculations show that the influence of the solvent methanol on the reaction is mainly on the step of acetylene coordination. Enhanced hydrogen bonding is the reason for acceleration of the reaction in protic solvent, which is supported by NBO charge analysis.更多还原