Studies of the polymerization of butadiene by titanium(IV) compounds with alkylaluminums

Abstract

AbstractCatalysts for the polymerization of butadiene consisting of an alkylaluminum compound with a titanium(IV) compound show variations in reactivity with Al/Ti ratio. The ratio at which maximum reactivity is obtained increases as the electronegativity of the ligands bound to titanium decreases. This is observed on replacement of the chloride ligands of titanium tetrachloride by either iodide or isopropoxy ligands. Catalysts prepared from titanium dichlorodiiodide or titanium chlorotriiodide behave like those from titanium tetraiodide, as would be expected from the previous observation that titanium is the preferred site of attachment for iodide in the reduction products of mixed salts. The cis content of the polymers obtained with the iodide‐containing salts can be 90% or more, but decreases with increasing titanium concentration, whereas the structure of polymers obtained with titanium tetrachloride is independent of catalyst concentration. Polymerization is not induced by either the soluble alkylaluminum compounds or the insoluble reduced titanium iodides which are produced by the reaction of triisobutylaluminum with titanium tetraiodide. The insoluble material can be activated by triisobutylaluminum or, less readily, by diisobutylaluminum iodide.