Reaction Electronic Flux as a Fluctuation of Relative Interatomic Electronic Populations

A methodological study concerning the mechanism of ethylene polymerization which is catalyzed by metallocene methyl cations bearing atoms from group IVB (Ti, Zr, and Hf) is presented. The derivative of relative interatomic electronic populations along the reduced reaction coordinate is used in order to reach consistency with the reaction electronic flux (REF). The polymerization under study was modeled following the CosseeArlman mechanism. A set of three reaction models that represent relevant elementary chemical reactions that defined the polymerization process (initiation, propagation, and termination) have been characterized by means of quantum chemical calculations. As a catalytic molecular model, the metallocene methyl cation which is built up by two cyclopentadienyl groups and one methyl group linked to the metal has been used in this study. The main goal was focused on getting detailed information about the catalytic reactions through the use of the tools mentioned above. As a result, it is revealed that there is a connection between the reaction electronic flux (a global descriptor) and the derivatives of relative interatomic electronic populations which are local descriptors, thus allowing us to better understand that reaction electronic flux is being governed by bond breaking and/or formation events.