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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Structurally Flexible Oxocarbenium/Borohydride Ion Pair: Dynamics of Hydride Transfer on the Background of Conformational Roaming
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Structurally Flexible Oxocarbenium/Borohydride Ion Pair: Dynamics of Hydride Transfer on the Background of Conformational Roaming

机译：结构柔性氧化羰烯鎓/硼氢化物离子对：氢化物转移动力学在构象漫游背景下

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We apply Born-Oppenheimer molecular dynamics to the practically significant [dioxane-H(+)-acetone]-[(C6F5)(3)B-H(-)] and [Et2O-H(+)-OCPr2][(C6F5)(3)B-H(-)] ion pair intermediates. Dynamics of hydride transfer in cation/anion ion pair takes place on the background of large amplitude configurational changes. Geometry of oxocarbenium/borohydride ion pairs is flexible, meaning that we uncover significant actual structural disorder at a finite temperature. Therefore, although the starting structure can be fairly close to the configurational area of the hydride transfer transition state (TS) and despite a low potential energy barrier (ca. 1.5 kcal/mol, according to the literature), already at T approximate to 325 K the system can remain ignorant of the TS region and move round and about ("roam") in the configurational space for a period of time in the range between 10 and 100 ps. This indicates structural flexibility of oxocarbenium/borohydride ion pair on apparently a flat potential energy "landscape" of cation/anion interaction, and this has not been taken into consideration by the free energy estimations in static considerations made thus far. The difference between the dynamics-based representation of the system versus the static representation amounts to the difference between quasi-bimolecular versus unimolecular descriptions of the hydride transfer step.
机译：我们应用玻恩 - 奥本海默分子动力学到几乎显著[二恶烷-H（+） - 丙酮] - [（C6F5）（3）BH（ - ）]和[Et 2 O中-H（+） - OCPr2] [（C6F5）（ 3）BH（ - ）]的离子对中间体。在阳离子/阴离子的离子对氢负离子转移的动态呈现的大振幅构变化的背景的地方。 oxocarbenium /硼氢化离子对几何形状是柔性的，这意味着我们揭开显著实际结构紊乱以有限的温度。因此，虽然起始结构可以是相当接近氢化物转移过渡态（TS）的构形区和尽管一个低势能垒（大约1.5千卡/摩尔，根据文献），已经在T接近于325 k中的系统可以保持昧TS区域的并且在构型空间移动轮与约（“漫游”），用于在所述范围内的一段10和100皮秒之间的时间。这表明对明显的平坦势能阳离子/阴离子相互作用的“风景” oxocarbenium /硼氢化离子对结构的灵活性，而这并没有被考虑到通过在静态考虑的自由能估计迄今所取得。该系统相对于静态表示的基于动态的表示之间的差别总计为准双分子相对于氢负离子转移步骤的单分子的描述之间的差。

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