Quadruple C–H Bond Activations of Methane by Dinuclear Rhodium Carbide Cation [Rh₂C₃]⁺

Abstract

The structure of the [Rh 2 C 3 ] + ion and its reaction with CH 4 in the gas phase have been studied by infrared photodissociation spectroscopy and mass spectrometry in conjunction with quantum chemical calculations. The [Rh 2 C 3 ] + ion is characterized to have an unsymmetrical linear [Rh–C–C–C–Rh] + structure existing in two nearly isoenergetic spin states. The [Rh 2 C 3 ] + ion reacts with CH 4 at room temperature to form [Rh 2 C] + + C 3 H 4 and [Rh 2 C 2 H 2 ] + + C 2 H 2 as the major products. In addition to the [Rh 2 C] + ion, the [Rh 2 13 C] + ion is formed at about one-half of the [Rh 2 C] + intensity when the isotopic-labeled 13 CH 4 sample is used. The production of [Rh 2 13 C] + indicates that the linear C 3 moiety of [Rh 2 C 3 ] + can be replaced by the bare carbon atom of methane with all four C–H bonds being activated. The calculations suggest that the overall reactions are thermodynamically exothermic, and that the two Rh centers are the reactive sites for C–H bond activation and hydrogen atom transfer reactions.

Combined molecular dynamics and coordinate driving method for automatically searching complicated reaction pathways

“…Similar procedures have been used in other works involving conformational space sampling. [53][54][55] Generally, MD simulation does not outperform Monte-Carlo based methods or genetic algorithms for global optimization tasks. [56][57][58][59][60][61] However, the more important task is to search for spatial orientations of reactive sites that lead to chemical reactions.…”

Activation of Methane by Rhodium Clusters on a Model Support C20H10

“…Distinctly, the acetonitrile (CH 3 CN) ligand was found to switch the mechanism of methane activation mediated by diatomic cation ZnO + , ultimately resulting in the improvement of product selectivity at the expense of activity. In sharp contrast with the extensively investigated single-metal systems, the preparation and reactivity study of the ligated or “supported” metal clusters, which represent important classes of heterogeneous ,,− catalysts for many reactions, were rarely investigated in the gas phase, despite that a considerable number of free metal clusters and metal compound (oxide, carbide, nitride, and boride) clusters being capable of activation and functionalization of methane under mild conditions have been reported in the literature. ,,− ,− …”

Methane Activation by [OsC3]+: Implications for Catalyst Design

“…In contrast to the abundant reports of catalytic experiments in the condensed phase, study of the mechanistic aspects encounters impediments due to the morphological heterogeneity of the active centers and the uncertain chemical environment. For this reason, gas-phase study of methane activation by metal carbides turns to be an effective way to determine the mechanisms and address the structure–performance relationship at a molecular level. , Thus, a series of metal carbide cluster ions, such as MC + (M = Sc, Ti, V, Cr, Cu, or Zn), CuC + , AuC + , FeC 3 – , IrC 3 + , PtC 3 + , FeC 4 + , FeC 6 – , MoC + , , Rh 2 C 3 + , and Ta 2 C 4 – , have been reacted with methane in the gas phase. Great efforts have been made to determine how the H 3 C–H bond is broken.…”

“…For this reason, gas-phase study of methane activation by metal carbides turns to be an effective way to determine the mechanisms and address the structure−performance relationship at a molecular level. 9,10 Thus, a series of metal carbide cluster ions, such as MC + (M = Sc, Ti, V, Cr, Cu, or Zn), 11 CuC + , 12 AuC + , 13 FeC 3 − , 14 IrC 3 + , 15 PtC 3 + , 15 FeC 4 + , 16 FeC 6 − , 17 MoC + , 18,19 Rh 2 C 3 + , 20 and Ta 2 C 4 − , 21 have been reacted with methane in the gas phase. Great efforts have been made to determine how the H 3 C−H bond is broken.…”

“…Great efforts have been made to determine how the H 3 C–H bond is broken. In general, the H 3 C–H bond can be activated in three manners: proton-coupled electron transfer (PCET), − hydrogen atom transfer (HAT), and hydride transfer (HT). − However, less instruction has been provided on catalyst design toward efficient methane conversion in the condensed phase. As one of the few examples, FeC 6 – shows monofunctional activity in non-oxidative methane aromatization, and the associated origins are instructive in terms of improving the corresponding condensed-phase catalysts.…”