Ab initio SCF calculations of 3P Mg and Be atom activation of methane

Abstract

In studying the insertion of metal atoms into CH bonds, ab initio molecular orbital calculations were used to obtain the energies and geometries of the reaction products methylmagnesium hydride (CH 3MgH) and methylberyllium hydride (CH 3BeH). The two species were successfully geometry-optimized in their respective ground states and in their lowest-lying excited triplet states: 7 a 1 13e 1 for the Mg-system (3-21G) and 5 a 1 12 e 1 for the Be-species (3-21G, 6-31G*). In both systems it was revealed that the excited states behaved like two weakly interacting species, the metal hydride and methyl radical moieties. This was in contrast to the ground state molecules which exhibited much shorter metal—carbon bonds. Investigations of possible reaction pathways involving different approaches of the 3 P Mg and Be atoms with respect to a methane molecule were carried out. No transition states or meta-stable species were found for any one of four specific approaches examined at the 3-21G level of sophistication but energy minima were obtained for each geometry in the context of restricted symmetry.