Polymer-incorporated iron catalysts for ethylene polymerization—a new approach to immobilize iron olefin catalysts on polystyrene chains

Abstract

2,6-Bis(imino)pyridyl iron catalysts bearing allyl groups [ArNC(Me)][Ar′NC(Me)]C₅H₃NFeCl₂ (Ar = Ar′ = 4-allyl-2,6-(i-Pr)₂C₆H₂ (Cat-1); Ar = 2,6-(i-Pr)₂C₆H₃, Ar′ = 4-allyl-2,6-(i-Pr)₂C₆H₃ (Cat-2)) have been synthesized and characterized. The corresponding polymer-incorporated iron catalysts PC-1, PC-2 and their SiO₂-supported core–shell structure catalysts SC-1 and SC-2 were obtained by the co-polymerization of the olefin groups of Cat-1 or Cat-2 with styrene in the presence of a radical initiator. All three types of catalysts (Cat-1 and Cat-2; PC-1 and PC-2; SC-1 and SC-2) have been investigated for ethylene polymerization. As a result, these catalysts were found to exhibit high activity using modified methylaluminoxane (MMAO) as a co-catalyst. Among them, the polymer-incorporated SiO₂ core–shell catalysts displayed very high activity (∼3181 g (mmol Fe)⁻¹ h⁻¹) with product molecular weights in the range 25–93 × 10⁴. The particle morphology of polyethylene produced by the core–shell structure catalysts (SC-1 and SC-2) was improved.