Wu Xiao-Nan, Liu Zizhuang, Wu Hechen, Zhang Di, Li Wei, Huang Zejian, Wang Guanjun, Xu Fuxing, Ding Chuan-Fan, Zhou Mingfei
Department of Chemistry, Collaborative Innovation Center of Chemistry for Energy Materials, Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials, Fudan University, Shanghai 200433, China.
J Phys Chem A. 2020 Apr 2;124(13):2628-2633. doi: 10.1021/acs.jpca.0c00371. Epub 2020 Mar 23.
The reactions of iridium- and osmium-carbyne hydride cations [HIrCH] and [HOsCH] with ethylene have been studied using mass spectrometry with isotopic-labeling in the gas phase. The carbyne reactivity is compared with that of the rhodium, cobalt, and iron analogues [TMCH] (TM = Fe, Co, and Rh), which were determined to have the carbene structures. Besides the cycloaddition/dehydrogenation reaction in forming the [TMCH] + H (TM = Ir and Os) products, a second reaction pathway producing the [TMCH] ion and CH via triple hydrogen atom transfer reactions to the carbyne carbon is observed to be the major channel. The latter channel is not observed in the rhodium, cobalt, and iron carbene cation reactions. Quantum-chemical calculations indicate that the distinct reactivity is not due to different initial structures of the reactants. Both reaction channels are predicted to be thermodynamically exothermic and kinetically facile for the carbyne cations, and the reactions proceed with the initial formation of a carbene intermediate via hydride-carbyne coupling. The latter channel is also exothermic but kinetically unfavorable for the rhodium, cobalt, and iron carbene cations.
利用气相同位素标记质谱法研究了铱和锇卡拜氢阳离子[HIrCH]和[HOsCH]与乙烯的反应。将卡拜的反应活性与铑、钴和铁类似物[TMCH]（TM = Fe、Co和Rh）的反应活性进行了比较，已确定这些类似物具有卡宾结构。除了形成[TMCH] + H（TM = Ir和Os）产物的环加成/脱氢反应外，还观察到通过向卡拜碳进行三次氢原子转移反应生成[TMCH]离子和CH的第二条反应途径是主要通道。在铑、钴和铁卡宾阳离子反应中未观察到后一种通道。量子化学计算表明，不同的反应活性并非由于反应物的初始结构不同。对于卡拜阳离子，预计两条反应通道在热力学上都是放热的，在动力学上都是容易进行的，并且反应通过氢化物-卡拜偶联首先形成卡宾中间体进行。后一种通道也是放热的，但对于铑、钴和铁卡宾阳离子在动力学上是不利的。
