Activation of carbon-hydrogen bonds by complexes involving multiply bonded Group 13 elements

Abstract

In the present research, Group 13 dimetallene complexes have been modeled for the activation of carbon-hydrogen bonds in small molecules using dispersion-corrected DFT calculations. It has been hypothesized that Group 13 multiple bonds, namely those between aluminum, can be extremely reactive due to the Lewis acidity of the metals and the high singlet biradical character of triel–triel bonds. Interestingly, from MCSCF (multiconfiguration SCF) calculations, it was found these molecules lack high levels of biradical character and contain 92% double bond character. Despite this, it was calculated that the activation of toluene with these dimetallene catalysts have reasonable free energy barriers as low as 30 kcal/mol with gallium being the most favorable among the Group 13 elements studied. Various substitutions made on the peripheral ligands of the catalyst models made little impact, but substitutions on the toluene being activated showed a decrease in energy barriers. The results give insight into the design of molecules containing Group 13 multiple bonds to activate carbon-hydrogen bonds.