Reactivity of First-Row Transition Metal Monocations (Sc super(+), Ti super(+), V super(+), Zn super(+)) with Methyl Fluoride: A Computational Study

• Published in: The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory Vol. 117; no. 14; pp. 2932 - 2943-2932-2943
• Main Authors: Redondo, Pilar, Varela-Alvarez, Adrian, Rayon, Victor Manuel, Largo, Antonio, Sordo, Jose Angel, Barrientos, Carmen
• Format: Journal Article
• Language: English
• Published: 01-04-2013
• Subjects: Cations; Fluorides; Fluorine; Rate constants; Reaction kinetics; Scandium; Titanium; Transition metals
• ISSN: 1089-5639; 1520-5215
• DOI: 10.1021/jp400366k

The gas-phase reactivity of methyl fluoride with selected first-row transition metal monocations (Sc super(+), Ti super(+), V super(+), and Zn super(+)) has been theoretically investigated. Our thermochemical and kinetics study shows that early transition-metal cations exhibit a much more active chemistry than the latest transition metal monocation Zn super(+). The strong C-F bond in methyl fluorine can be activated by scandium, titanium, and vanadium monocations yielding the metal fluorine cation, MF super(+). However, the rate efficiencies vary dramatically along the period 0.73 (Sc), 0.91 (Ti), and 0.028 (V) in agreement with the experimental observation. The kinetics results show the relative importance of the entrance and exit channels, apart from the "inner" bottleneck, to control the global rate constant of these reactions. At the mPW1K/QZVPP level our computed k sub(global) (at 295 K), 1.99 10 super(-9) cm super(3) molecule super(-1) s super(-1) (Sc super(+)), 1.29 10 super(-9) cm super(3) molecule super(-1) s super(-1) (Ti super(+)), and 3.46 10 super(-10) cm super(3) molecule super(-1) s super(-1) (V super(+)) are in good agreement with the experimental data at the same temperature. For the reaction of Zn super(+) and CH sub(3)F our predicted value for k sub(outer), at 295 K, 3.79 10 super(-9) cm super(3) molecule super(-1) s super(-1), is in accordance with the capture rate constant. Our study suggests that consideration of the lowest excited states for Ti super(+) and V super(+) is mandatory to reach agreement between calculations and experimental measurements.