Reactions of superelectrophilic BH2+, BCl2+ and AlCl2+ with carbonyl compounds and alkenes1

Abstract

Density functional theory (DFT) method was employed to investigate the reactions of superelectrophilic BH 2 + , BCl 2 + and AlCl 2 + with carbonyl compounds (formaldehyde, acetaldehyde) and alkenes (ethene, propene). Addition to BH 2 + with formaldehyde and acetaldehyde first give exothermically O-coordinated allylic type structures. Subsequent hydride shifts from BH 2 group to the carbonyl carbon were also calculated to be exothermic. However, the processes have considerable kinetic barrier. Similar reactions of BCl 2 + and AlCl 2 + were also studied. Reactions of BH 2 + , BCl 2 + and AlCl 2 + with alkenes (ethene, propene) were also computed and compared with the results obtained with those of formaldehyde and acetaldehyde.

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

“…This reaction step is the only one reported by Olah et al in their recent theoretical study of the reactions of BH 2 + with alkenes at the B3LYP/6-311+G(d,p) level. 15 Their results agree with ours; however, the stability of structure 4a seems to be overestimated by about 10 kcal/mol in their report. On the other path, the B 1 -C 7 bond in 4a breaks, going through transition states 4tsab and 4tsbc and minimum 4b involving a series of hydrogen shifts (see Figure 7) to form 4c.…”

“…In the first pathway, H 2 in compound 4a shifts from B 1 to C 7 and the B 1 −C 7 and B 1 −H 2 bonds break to form 4c through 4tsac . This reaction step is the only one reported by Olah et al in their recent theoretical study of the reactions of BH 2 + with alkenes at the B3LYP/6-311+G(d,p) level . Their results agree with ours; however, the stability of structure 4a seems to be overestimated by about 10 kcal/mol in their report.…”

“…14 In addition, Olah and co-workers recently reported calculations on a series of BH 2 + reactions with neutrals containing double bonds including C 2 H 4 and C 3 H 6 , as well as H 2 CO and H 3 CCHO; however, they focused only on a minuscule part of the potential energy surface, which included only the initial reaction complex and a hydride transfer process. 15 Finally, the reactions of Al + with H 2 and small hydrocarbons were also reported recently 16 in an attempt to investigate the possibility of insertion of this ion, isovalent with B + . However, the experiments failed to obtain HAlH + and calculations suggest that the formation of this ion from Al + and H 2 is endothermic, despite the fact that it is a minimum in the potential energy surface.…”

“…Similar deficiencies are found in the potential energy surface for the reaction of BH 2 + with C 2 H 2 reported by the same authors . In addition, Olah and co-workers recently reported calculations on a series of BH 2 + reactions with neutrals containing double bonds including C 2 H 4 and C 3 H 6 , as well as H 2 CO and H 3 CCHO; however, they focused only on a minuscule part of the potential energy surface, which included only the initial reaction complex and a hydride transfer process …”

Efficient Chemoselective Carboxylation of Aromatics to Arylcarboxylic Acids with a Superelectrophilically Activated Carbon Dioxide−Al2Cl6/Al System

“…In our previous work using superacidic conditions, aromatics such as benzene with carbon dioxide gave mainly benzophenone, indicating that any intermediate benzoic acid formed under the reaction conditions reacts further, thus benzoylating excess benzene 12a…”