The catalytic mechanism of H2 activation by a carbenoid aluminum compound is analyzed in great detail. On the basis of the reaction force analysis, the electronic activity that takes place during the chemical reaction was identified and characterized through the reaction electronic flux and rationalized in terms of chemical events that drive the reaction. Successive transformation of the nucleophilic or electrophilic character of the reagents along the reaction coordinate monitored through the dual descriptor allows us to obtain a very complete and detailed description of the reaction mechanism that proceeds through a two-stage mechanism in a one-kinetic-step process.