Infrared Spectra of IrCCH2, HIrCCH, and Ir-η2-C2H2 Prepared in Reaction of Laser-Ablated Iridium Atom with Acetylene

Iridium Dimer Anion-Mediated C≡C Triple Bond Cleavage and Successive Dehydrogenation of Acetylene in the Gas Phase

The reactions of the iridium dimer anion [Ir₂]^- with acetylene have been studied by mass spectrometry in the gas phase, which indicate that the [Ir₂]^- anion can consecutively react with C₂H₂ molecules to form the [Ir₂C_2x]^- (x = 1, 2) and [Ir₂C_2yH₂]^- (y = 3-5) anions as major products with the successive release of H₂ molecules at room temperature. The reactions are confirmed by the reactions of the mass-selected product [Ir₂C₂]^- anion with C₂H₂ to produce [Ir₂C₄]^- and [Ir₂C_2yH₂]^- (y = 3-5). Photoelectron spectra and quantum chemistry calculations confirm that the [Ir₂C_2x]^- (x = 1, 2) product anions possess cyclic [Ir(μ-C)₂Ir]^- and [Ir(μ-C)(μ-C₃)Ir]^- structures, implying that the robust C≡C triple bond of acetylene can be completely cleaved by the [Ir₂]^- anion.

C/C Exchange in Activation/Coupling Reaction of Acetylene and Methane Mediated by Os+: A Comparison with Ir+, Pt+, and Au. J Phys Chem Lett 2020;11:8346-8351. [PMID: 32885973 DOI: 10.1021/acs.jpclett.0c02068]

The activation and coupling reactions of methane and acetylene mediated by M⁺ (M = Os, Ir, Pt, and Au) have been comparatively studied at room temperature by the techniques of mass spectrometry in conjunction with theoretical calculations. Studies have shown that Os⁺ and Ir⁺ can mediate the activation/coupling reaction of CH₄ and C₂H₂, while Pt⁺ and Au⁺ cannot, which could be explained by the number of empty valence orbitals in the metal atom. In addition, there are different competition channels for the reaction mediated by Os⁺ and Ir⁺: an expected dehydrogenation and an unexpected C/C exchange. We find that if the rare C/C exchange reaction takes place, there are symmetric carbon atoms in the reaction intermediate and the C/C exchange reaction is favored kinetically. The C/C exchange reaction must be considered, which will affect the yield of the products in the primary reaction. This study shows the molecular-level mechanisms which include the C/C exchange reaction in the activation and coupling reaction of organic compounds mediated by different metals.

Observation of Spontaneous C=C Bond Breaking in the Reaction between Atomic Boron and Ethylene in Solid Neon

A ground-state boron atom inserts into the C=C bond of ethylene to spontaneously form the allene-like compound H2 CBCH2 on annealing in solid neon. This compound can further isomerize to the propyne-like HCBCH3 isomer under UV light excitation. The observation of this unique spontaneous C=C bond insertion reaction is consistent with theoretical predictions that the reaction is thermodynamically exothermic and kinetically facile. This work demonstrates that the stronger C=C bond, rather than the less inert C-H bond, can be broken to form organoboron species from the reaction of a boron atom with ethylene even at cryogenic temperatures.