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首页> 外文期刊>Organometallics >Intramolecular coupling of eta(2)-iminoacyls on zirconium bis(aryloxides) and calix[4]arenes: Revised mechanism by DFT calculations and Car-Parrinello molecular dynamics simulations
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Intramolecular coupling of eta(2)-iminoacyls on zirconium bis(aryloxides) and calix[4]arenes: Revised mechanism by DFT calculations and Car-Parrinello molecular dynamics simulations

机译：双（芳氧基）锆和杯[4]芳烃上eta（2）-亚氨基酰基的分子内偶联：通过DFT计算和Car-Parrinello分子动力学模拟修正的机理

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The intramolecular coupling of the two iminoacyl units in the bis(eta(2)-iminoacyl) complexes [calix[4](OMe)(2)(O)(2)-Zr(eta(2)-MeCNBUt)(2)] and [(2,6-(BU2C6H3O)-C-t)(2)-Zr(eta(2)-MeCNPh)(2)] to generate the corresponding enediamido species has been investigated by means of both static and dynamic density functional calculations. For both systems we have characterized the stationary points of the potential energy surfaces for the coupling reaction and evaluated the overall energy profile. Car-Parrinello molecular dynamics simulations have been performed to gain insight into the detailed mechanistic features of the iminoacyl coupling and surprisingly show that this reaction occurs through an asynchronous reaction mechanism in which a decoordinated iminoacyl attacks the residual coordinated iminoacyl C-N double bond. A transition state search, performed without any symmetry constraint, led to structures consistent with the proposed mechanism 23.8 and 21.2 kcal mol(-1) above the starting his(eta(2)-iminoacyl) reagents, in good agreement with experimental activation enthalpies. On the basis of the proposed reaction mechanism we are also able to reproduce the activation energy of the coupling reaction with electron-withdrawing substituents on the iminoacyl moiety. Inspection of the electronic structure changes along the proposed reaction pathway suggests that the iminoacyl coupling process can be described as an intramolecular attack of the decoordinated iminoacyl carbon lone-pair at the coordinated iminoacyl pi* orbital, thus reconciling the iminoacyl coupling reaction mechanism with the generally accepted pattern of acyl and iminoacyl reactivity.
机译：双（eta（2）-亚氨基酰基）复合物中的两个亚氨基酰基单元的分子内偶联[calix [4]（OMe）（2）（O）（2）-Zr（eta（2）-MeCNBUt）（2） ]和[（2,6-（BU2C6H3O）-Ct）（2）-Zr（eta（2）-MeCNPh）（2）]已通过静态和动态密度泛函计算进行了研究。对于这两种系统，我们都已表征了用于偶联反应的势能面的固定点，并评估了整体能量分布。已经进行了Car-Parrinello分子动力学模拟，以深入了解亚氨基酰基偶联的详细机械特征，并出人意料地表明，该反应是通过异步反应机制发生的，在该机制中，未配位的亚氨基酰基攻击残余的配位的亚氨基酰基C-N双键。在没有任何对称性约束的情况下进行的过渡状态搜索导致结构与起始his（eta（2）-iminoacyl）试剂上方拟议的机制23.8和21.2 kcal mol（-1）一致，与实验活化焓高度吻合。在提出的反应机理的基础上，我们还能够再现亚氨基酰基部分上具有吸电子取代基的偶联反应的活化能。检查沿提议的反应途径的电子结构变化表明，亚氨基酰基偶联过程可描述为在亚氨基酰基π*配位轨道上未配位的亚氨基酰基碳孤对的分子内攻击，从而使亚氨基酰基偶联反应机理与一般可接受的酰基和亚氨基酰基反应性模式。

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