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Influence of the para-substitution in bis(arylimino)pyridine iron complexes on the catalytic oligomerization and polymerization of ethylene

“…Deprotonation of the iminomethyl groups [37][38][39], reduction of the metal centers [40][41][42], addition of nucleophiles to the imino carbon atoms to give amido complexes [38,43], reductive dimerization at the iminomethyl groups [44,45], alkylation at the pyridine C-2 or C-4 carbon atoms [43,46] and even at the pyridine nitrogen atom [47][48][49] were observed depending on the applied nucleophilic reagent and the reaction conditions. Since the acidities of the iminomethyl protons and the fluorenyl protons (for free fluorene pK a = 22.9) [50] seem to be similar, both positions may be deprotonated in complexes 30-32. Probably, the competition of these two groups is the reason, why no clean complexation reactions were observed after addition of zirconium tetrachloride or the half-sandwich complex cyclopentadienylzirconium trichloride.…”