Density functional investigation of incorporation of functional additives to neutral salicylaldiminato Ni(II) polymerization catalyst

A recent density functional study by Chan et al. (Organometallics 19 (2000) 2741) on the mechanism of ethylene polymerization using neutral Ni(II) salicylaldiminato catalysts revealed that there is no direct correlation between activation energy required for ethylene insertion to NiC (alkyl) bond and reported turnover frequency (TOF). With this background using density functional method (B3LYP/LANL2DZ), an attempt has been made to investigate the variation in TOF due to incorporation of functional additives in the neutral Ni(II) salicylaldiminato catalyzed polymerization of ethylene. Reasonably good correlation is observed between ln(TOF) of the catalysts on the one hand, and NiO (additive) bond dissociation energy or the topological parameters of electron density of the NiO (additive) bond on the other. Taking this correlation and comparison of orbital interactions of various species involved into account, a probable mechanism for ethylene polymerization in the presence of the additives is suggested.