Computational Study of the Reactions of BH₂⁺ with H₂, Methane, Ethane, Ethylene, and Acetylene in the Gas Phase

Abstract

We have studied the potential energy surface for the reactions of BH 2 + with H 2 , methane, ethylene and acetylene at the CCSD(T)/cc-pVTZ//MP2(full)/cc-pVTZ level and the reaction of BH 2 + with ethane at the CCSD(T)/ 6-311G(d,p)//MP2(full)/6-311G(d,p) level of theory. A complete survey of the potential energy surfaces is presented and the structures of the stationary points and the mechanisms of these reactions are discussed. The calculations suggest that the products of these reactions are formed by addition and elimination of a hydrogen molecule, effectively activating the carbon-hydrogen bond. Furthermore, theory also suggests that elimination of HD is the sole product in the reaction of BD 2 + with ethane; however, H/D scrambling occurs to some extent in the reaction with acetylene whereas it is complete in the reaction with ethylene. Therefore, loss of H 2 , HD, and D 2 is predicted, in agreement with experiments. In addition, elimination of CH 4 can also be produced in the reaction of BH 2 + with ethane, even with BD 2 + as reactant. Although the products of the carbon-carbon bond activation are also exothermic in the reactions of acetylene and ethylene, they are prevented kinetically. The remarkable electrophilic properties of BH 2 + are presented and discussed as well as details on the bonding structure of the three-center two-electron bonds characteristic of these compounds.

The Conversion of Methane to Methanol: A Reaction Catalyzed by I+ or I2+?

“…22 It has also been observed with other electrophiles, such as in the reaction of BH 2 + with CH 4 and C 2 H 6 . 23,24 In addition to CH 2 I + , Mayhew et al also observed CH 3 I + although with a small branching ratio (14%). 19 We do not observe this reaction channel unless the helium flow in the reaction flow tube is reduced considerably; only under these conditions is a small but noticeable peak corresponding to CH 3 I + observed.…”

Theoretical Study of the Chemoselectivity of Tungsten-Dependent Acetylene Hydratase

“…The reactivities of ethylene and acetylene have been demonstrated to be quite similar in many different types of reactions. − Quantum chemical calculations have been used to compare the relative reactivities in, for example, cycloaddition, , phosphinidene addition, sulfur addition, borohydride cation addition, hydration on zeolite, and ylidic radical addition . The barriers for these reactions were found to be rather close between ethylene and acetylene, with the largest difference on the order of 4 kcal/mol.…”

Superelectrophilic Intermediates in Nitrogen-Directed Aromatic Borylation

“…Related hypervalent species may be involved in high temperature hydrogen transfer reactions catalyzed by trialkyl boranes, the recent hydrogen activation experiments of Stephan et al and related studies, and gas phase equilibria involving BH 2 (+), H 2 , and BH 4 (+) . The relationship between 38 and 16a has a close parallel in the cationic ammonia borane derivatives [H 3 N•BH 4 ] + (borenium ion hydrogen adduct) and [H 3 N•BH 2 ] + (borenium ion), structures that have been evaluated computationally …”