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为了探寻OsO+与H2气相反应的机理,用密度泛函理论方法 UB3LYP,全优化了该反应的加成(氧化加成和[2+2]环加成)-消除、氢抽提-反弹,以及氧端插入等四种可能路径中所有可能的反应物、中间体、过渡态和产物在六重态、四重态和二重态等三个自旋态下的几何结构,计算了各种机理反应的势能面.结果表明,标题反应为自旋禁阻反应,反应起始自四重态,最终产物为六重态基态,整个反应放热21.0 kJ mol-1.因反应络合物相对于入口通道有太正Gibbs函数,氧端插入机理是高能的过程.其他三种机理都具有多(或二)态反应性(MSR或TSR).其中,两种加成-消除机理的最低能量路径都可能经由四重态-二重态-四重态-六重态的三次自旋翻转,抽提-反弹机理的最低能量路径可能经历由四重态-六重态的自旋翻转.抽提-反弹机理由势能面一路攀升的吸热氢抽提过程和几乎无能垒的强放热的反弹过程组成,所以按该机理反应在常温常压下难以发生.两种加成-消去机理的决速步(第二个H的迁移步)相同,虽然其位垒稍高,为156.9 kJ mol-1,但与其进程中前面的强放热步骤耦合,常温常压下该反应是可以发生的.其中,协同环加成步的位垒仅28.7 kJ mol-1,比第一个H的还原消去步的位垒低113.7 kJ mol-1,所以竞争的结果是,常温常压下[2+2]环加成-消去机理比氧化加成-消去机理在动力学上更有利.
In order to explore the mechanism of gas-phase reaction between OsO + and H2, the reaction of addition (oxidative addition and [2 + 2] cycloaddition) -immobilization, hydrogen extraction-bouncing was fully optimized using the density functional theory method UB3LYP Oxygen insertion and all four possible paths of possible reactants, intermediates, transition states and products in the six-state, quadruple state and the triplet state of three spin geometry, the calculation of the various mechanisms The results show that the title reaction is a spin-forbidden reaction, the reaction starts from the quadruple state, and the final product is a six-state ground state, the entire reaction exotherm 21.0 kJ mol-1. Because of the reaction complex relative to The entrance channel has too positive Gibbs function and the oxygen insertion mechanism is a high-energy process. The other three mechanisms have multi-or two-state reactivity (MSR or TSR), of which the two energy addition-elimination mechanisms have the lowest energy path All possible via the triple-spin of the quadruplet-quartet-quartet-hexatom, the lowest energy path of the extractive-rebound mechanism may undergo spin-inversion from the quadruplet-hexastronic state. - The bounce-back mechanism increases with the absorption of endothermic hydrogen from the potential energy surface and from the strong exothermic rebound with almost no barrier Therefore, according to this mechanism, the reaction is hard to occur under normal temperature and pressure.The velocity-increasing steps of the two addition-elimination mechanisms (the second H migration step) are the same, although the barrier is slightly higher at 156.9 kJ mol- 1, but coupled with the previous strong exothermic step in the process, the reaction can take place under normal temperature and pressure, in which the potential barrier of the cooperative cycloaddition step is only 28.7 kJ mol-1, which is lower than that of the first H The step barrier is 113.7 kJ mol-1, so the competitive result is that the [2 + 2] cycloaddition-elimination mechanism is more kinematically advantageous than the oxidative addition-elimination mechanism at ambient temperature and pressure.