The synthesis, spectroscopic characterisation and catalytic olefin polymerisation behaviour of a class of binuclear titanium bis(benzyl) complexes bearing bis-(pyridine-2-phenolate-6-methine)-[μ-(arylene-1,4-diyl-2,3-X)] ligands [X = -CH- (1), F (2), H (3)], and mononuclear analogues, are described. These bimetallic catalyst frameworks are designed to exhibit a degree of conformational flexibility, which is regulated by steric effects and crucially permits tuning of intermetallic distances and geometry, yet their shape-persistent nature can also confer favourable entropic terms. Complexes 1-3 are characterised as two diastereomers [ () and (,)] in ratios of 1.32, 1.18 and 1.13 respectively, according to H NMR spectroscopy. In contrast to 3, [H,H]-ROESY experiments for 1 and 2 revealed that the X substituents can impose preferred conformations with orientations of Ti centres and benzyl groups, thus implying that the activated catalysts would present binding sites with the same direction of access. For ethylene-(1-octene) copolymerisation reactions, in conjunction with [PhC][B(CF)], catalyst 1 displayed superior efficiencies and produced polymers with higher values and enhanced comonomer incorporation ratios (up to 41%), when compared with the mononuclear 5m (22%). These results are indicative of enhanced comonomer enchainment and cooperative reactivity by the Ti sites.
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