jp0c00371_si_001.pdf (2.27 MB)
Reactions of Transition-Metal Carbyne Cations with Ethylene in the Gas Phase
journal contribution
posted on 2020-03-23, 12:36 authored by Xiao-Nan Wu, Zizhuang Liu, Hechen Wu, Di Zhang, Wei Li, Zejian Huang, Guanjun Wang, Fuxing Xu, Chuan-fan Ding, Mingfei ZhouThe
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 [TMCH2]+ (TM = Fe, Co, and Rh), which
were determined to have the carbene structures. Besides the cycloaddition/dehydrogenation
reaction in forming the [TMC3H4]+ + H2 (TM = Ir and Os) products, a second reaction pathway
producing the [TMC2H2]+ ion and CH4 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.