Homo-polymerization of 1-hexene catalysed by OˆNˆN (Salicylaldimine)iron(III) pre-catalysts to branched poly(1-hexene)

Five new iron(III) 1-hexene polymerisation catalysts were prepared from the reactions of 2,4-di-tert-butyl-6-(2-(1H-imidazol-4-yl)ethylimino)methylphenol (L1), or 4-tert-butyl-6-(2-(1H- imidazol-4-yl)ethylimino)methylphenol (L2) or 2,4-di-tert-butyl-6-[(2-pyridin-2-yl-ethylimino)-methyl-phenol (L3) with anhydrous iron(II) halides to form [FeCl₂(L1)] (1), [FeBr₂(L1)] (2), [FeI₂(L1)] (3), [FeBr₂(L2)] (4) and [FeCl₂(L3)] (5). All the iron(III) complexes 1-5 were activated with EtAlCl2 to produce active catalysts for the polymerisation of 1-hexene to low molecular weight poly(1-hexene) (M_n = 1021-1084 Da) and very narrow polydispersity indices (1.19-1.24).¹H and¹³C{¹H} NMR analysis showed the polymers are branched with methyl, butyl and longer chain branches. The longer chain branches are dominant indicating that 2,1-insertion of monomer is favoured over 1,2-insertion in the polymerisation reaction.