Department of Chemistry, Graduate School of Nanoscience & Technology (WCU), KAIST, Center for Time-Resolved Diffraction, Daejeon 305-701, Republic of Korea.
J Phys Chem A. 2009 Oct 22;113(42):11382-9. doi: 10.1021/jp905158j.
Ti(+) is known to react with acetone (CH(3)COCH(3)) to produce TiO(+) and CH(2)CHCH(3) as products, but the detailed reaction mechanism and the most favorable reaction pathway have not yet been elucidated. Here, we investigate the doublet and quartet potential-energy surfaces associated with the gas-phase reaction between Ti(+) and acetone for three plausible pathways, (i) direct metal-ion insertion into the C=O bond, (ii) direct H shift, and (iii) metal-mediated H migration, by using the density functional theory (DFT) and ab initio methods. The molecular structures of intermediates and transition states involved in these reaction pathways are optimized at the DFT level by using the PBE0 functional. All transition states are identified by using the intrinsic reaction coordinate (IRC) method, and the resulting reaction coordinates describe how Ti(+) activates the C=O bond of CH(3)COCH(3) (acetone) and yields TiO(+) and CH(2)CHCH(3) (propene) as products. The intersystem crossing (ISC) point is optimized by a multireference ab initio method, and spin-orbit effects are considered around the ISC point. On the basis of the presented results, we propose that the most favorable reaction pathway proceeds via the direct metal-ion insertion into the C=O bond and passes through an ISC point.
Ti(+)与丙酮（CH(3)COCH(3)）反应生成 TiO(+)和 CH(2)CHCH(3)，但详细的反应机制和最有利的反应途径尚未阐明。在这里，我们通过使用密度泛函理论（DFT）和从头算方法，研究了 Ti(+)与丙酮在气相中三种可能的反应途径（i）直接金属离子插入 C=O 键，（ii）直接 H 迁移，和（iii）金属介导的 H 迁移，涉及的三重态和四重态势能面。通过使用 PBE0 函数在 DFT 水平上优化了这些反应途径中涉及的中间体和过渡态的分子结构。所有过渡态均通过内禀反应坐标（IRC）方法进行识别，所得反应坐标描述了 Ti(+)如何激活 CH(3)COCH(3)（丙酮）的 C=O 键，并生成 TiO(+)和 CH(2)CHCH(3)（丙烯）作为产物。ISC 点通过多参考从头算方法进行优化，并考虑了 ISC 点周围的自旋轨道效应。根据所提出的结果，我们提出最有利的反应途径是通过直接金属离子插入 C=O 键并通过 ISC 点进行。
