Cyclotrimerization of Acetylene in Gas Phase V+(C2H2) n Complexes: Detection of Intermediates and Products with Infrared Spectroscopy

• Published in: The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory Vol. 123; no. 31; pp. 6733 - 6743
• Main Authors: Marks, Joshua H, Ward, Timothy B, Brathwaite, Antonio D, Ferguson, Sojourna, Duncan, Michael A
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 08.08.2019
• Subjects: Chemistry; Physics
• ISSN: 1089-5639; 1520-5215
• DOI: 10.1021/acs.jpca.9b04962

Infrared laser spectroscopy and mass spectrometry were used to determine the structures of intermediates and products in the single-atom-catalyzed trimerization of acetylene to form benzene. Complexes of the form V+(C2H2) n were produced in the gas phase via laser ablation in a pulsed-nozzle source, size-selected with a mass spectrometer, and studied with infrared laser photodissociation spectroscopy. Density functional theory calculations were performed in support of the experiments. Single- and double-acetylene complexes form V+(C2H2) n metallacycle structures. Three-acetylene complexes exhibit a surprising dependence on the acetylene concentration, forming V+(C2H2)3 and (C2H2)­V+(C4H4) tri- and dimetallacycle ion structures at low concentrations and eventually V+(benzene) at higher concentrations. These observations reveal intermediates along the reaction path of acetylene cyclotrimerization to benzene.