Activation of Methane by Os+: Guided-Ion-Beam and Theoretical Studies
Activation of Methane by Os+: Guided-Ion-Beam and Theoretical Studies
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DOI：
10.1002/cplu.201300147
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发表时间：
2013-09-01
期刊：
影响因子：
3.4
通讯作者：
Citir, Murat
中科院分区：
文献类型：
--
作者：
Armentrout, P. B.;Parke, Laura;Citir, Murat
第三行过渡金属阳离子Os+活化甲烷的实验研究通过检查的动能依赖的Os+与CH 4和CD 4的反应，使用引导离子束串联质谱。流管离子源产生处于其电子基态且主要处于基态自旋轨道能级的Os+。脱氢形成[Os，C，2 H]（+）+H-2是放热的、有效的，并且是在低能量下观察到的Os+与甲烷反应的唯一过程，而奥什+在较高能量下主导产物谱。分析了几个吸热反应的截面的动能依赖性，得到0 K键离解能（以eV计）为D-0（Os+C）=6.20 +/- 0.21、D-0（Os+CH）=6.77 +/- 0.15和D-0（Os+ CH 3）=3.00 +/- 0.17。因为它是以电子方式形成的，所以D-0（Os+ CH 2）必须大于4.71eV，而推测性的解释则认为电子的电子性超过0.6eV。B3 LYP/def 2-TZVPP水平上的量子化学计算显示与实验键能和先前可用的理论值有合理的一致性。理论还提供了产物种类的电子结构以及中间体和过渡态沿着反应势能面。值得注意的是，脱氢产物的结构被预测为HOsCH+，而不是OsCH 2+，与以前的工作相反。
Activation of methane by the third-row transition-metal cation Os+ is studied experimentally by examining the kinetic energy dependence of reactions of Os+ with CH4 and CD4 using guided-ion-beam tandem mass spectrometry. A flow tube ion source produces Os+ in its electronic ground state and primarily in the ground spin-orbit level. Dehydrogenation to form [Os,C,2H](+)+H-2 is exothermic, efficient, and the only process observed at low energies for reaction of Os+ with methane, whereas OsH+ dominates the product spectrum at higher energies. The kinetic energy dependences of the cross sections for several endothermic reactions are analyzed to give 0K bond dissociation energies (in eV) of D-0(Os+C)=6.20 +/- 0.21, D-0(Os+CH)=6.77 +/- 0.15, and D-0(Os+CH3)=3.00 +/- 0.17. Because it is formed exothermically, D-0(Os+CH2) must be greater than 4.71eV, and a speculative interpretation suggests the exothermicity exceeds 0.6eV. Quantum chemical calculations at the B3LYP/def2-TZVPP level show reasonable agreement with the experimental bond energies and with previous theoretical values available. Theory also provides the electronic structures of the product species as well as intermediates and transition states along the reactive potential energy surfaces. Notably, the structure of the dehydrogenation product is predicted to be HOsCH+, rather than OsCH2+, in contrast to previous work.