Mechanism of methane activation by electrophiles generated in the AlBr5 system: An MNDO/PM3 study of the potential energy surface of the [AlBr5+CH4] system

Fragments of the potential energy surfaces (PES) of the AlBr₅ (I) and AlBr₅+CH₄] (II) systems were studied by the MNDO/PM3 method. Five local minima corresponding to Br₂·AlBr₃ donor-acceptor complexes were found on the PES of system I. Two of these complexes have a pronounced ionic character. In system II, among the products of barrierless addition of Br₂·AlBr₃ complexes to CH₄, the methane molecule is activated only in two complexes. These are products of the attack of the most electrophilic AlBr₅ complexes on a H atom of the methane molecule. The potential barriers to conversion of these products into complexes with structures formally corresponding to the products of the attack of electrophiles on a C−H bond (the Olah scheme) or the C atom of methane molecule (the Schreiner scheme) were calculated. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 802–808, May, 2000.