Bimetallic phenylene-bridged Cp/amide titanium complexes and their olefin polymerization

Abstract

Bimetallic dichlorotitanium complexes, {2,6-[η⁵-2,5-Me₂C₅H₂]₂-4-R-C₆H₂N-µN}{Ti(IV)Cl₂}₂ (7, R = Me; 8, R = F) and 4,4′-A[{2-(η⁵-2,3,5-Me₃C₅H)C₆H₃NC₆H₁₁-κN}Ti(IV)Cl₂]₂ (18, A = CH₂; 19, A = O; 20, A = ortho-C₆H₄) are prepared via a key step of the Suzuki-coupling reaction of 2-dihydroxyboryl-3-methyl-2-cyclopenten-1-one (1) with dibromo-compounds. The solid state structure of 7 was determined by X-ray crystallography. Complexes 7 and 8 are not active for ethylene/1-hexene copolymerization. Meanwhile, the complexes 18–20 are highly active and their activities are higher than that of the mononuclear analogue, {2-(η⁵-2,3,5-Me₃C₅H)C₆H₃NC₆H₁₁-κN}Ti(IV)Cl₂ (21). The molecular weights of the polymers obtained with the bimetallic complexes 18–20 are higher than that of the polymer obtained using 21. Slightly higher contents of long-chain-branching are observed for the copolymers obtained using the bimetallic system.