o-Phenylene-bridged Cp/sulfonamido titanium complexes for ethylene/1-octene copolymerization

Abstract

The Suzuki-coupling reaction of 2-(dihydroxyboryl)-3,4-dimethyl-2-cyclopenten-1-one (1) and 2-(dihydroxyboryl)-3-methyl-2-cyclopenten-1-one (2) with 2-bromoaniline derivatives affords cyclopentenone compounds (3–8) from which cyclopentadiene compounds, 4,6-R′₂-2-(2,5-Me₂C₅H₃)C₆H₂NH₂ (9–11) and 4,6-R′₂-2-(2,3,5-Me₃C₅H₂)C₆H₂NH₂ (12–14) are prepared. After sulfonation of the –NH₂ group with p-TsCl, metallation is carried out by successive addition of Ti(NMe₂)₄ and Me₂SiCl₂ affording o-phenylene-bridged Cp/sulfonamido titanium dichloride complexes, [4,6-R′₂-2-(2,5-Me₂C₅H₂)C₆H₂NSO₂C₆H₄CH₃)]TiCl₂ (R′ = H, 21; R′ = Me, 22; R′ = F, 23) and [4,6-R′₂-2-(2,3,5-Me₃C₅H)C₆H₂NSO₂C₆H₄CH₃)]TiCl₂ (R′ = H, 24; R′ = Me, 25; R′ = F, 26). The molecular structures of 24 and [2-(2,5-Me₂C₅H₂)C₆H₄NSO₂C₆H₄CH₃)]Ti(NMe₂)₂ (27) are determined by X-ray crystallography. The Cp(centroid)–Ti–N angle in 24 is smaller (100.90°) than that observed for the CGC (constrained-geometry catalyst), [Me₂Si(η⁵-Me₄Cp)(N^tBu)]TiCl₂ (107.6°) indicating a more “constrained feature” in 24 than in the CGC. Complex 24 shows the highest activity among the newly prepared complexes in ethylene/1-octene copolymerization but it is slightly inferior to the CGC in terms of activity, comonomer-incorporation ability, and molecular weight of the obtained polymers.