Synthesis of Half-Titanocenes Containing Phenoxy-imine Ligands and Their Use as Catalysts for Olefin Polymerization

Abstract

Various half-titanocenes containing phenoxy-imine ligands of the type Cp‘TiCl2[O-2-R1-6-(R2NCH)C6H3] [Cp‘ = Cp* (C5Me5) and R1, R2 = Me, 2,6-iPr2C6H3 (1); tBu, 2,6-iPr2C6H3 (2); Me, tBu (3); tBu, tBu (4); Cp‘ = 1,2,4-Me3C5H2 and R1, R2 = Me, 2,6-iPr2C6H3 (5); Cp‘ = Cp and R1, R2 = Me, 2,6-iPr2C6H3 (6); Me, tBu (7)] were prepared by reaction of Cp‘TiCl3 with LiO-2-R1-6-(R2NCH)C6H3 that were prepared in situ by treating the corresponding phenol with n-BuLi. Cp*TiMe2[O-2-Me-6-{(2,6-iPr2C6H3)NCH}C6H3] (8) was prepared from Cp*TiMe3 by treating with 2-Me-6-{(2,6-iPr2C6H3)NCH}C6H3OH in n-hexane, and the reaction with [PhN(H)Me2][B(C6F5)4] was also explored. Structures for 1−3 and 5−8 were determined by X-ray crystallography, and the imino nitrogen in the phenoxy-imine ligand was not coordinated to Ti in all cases; the bond angles for Ti−O−C(Ph) were affected by substituents in both cyclopentadienyl and phenoxy-imine ligands. The catalytic activities for ethylene polymerization and syndiospecific styrene polymerization using 1−7−MAO catalyst systems were highly affected by the substituents in both cyclopentadienyl and phenoxy-imine ligands; the Cp* analogues (3, 4) exhibited notable activities for ethylene polymerization, whereas the Cp analogues (6, 7) showed significant activities for syndiospecific styrene polymerization. The Cp analogue 6 was also an effective catalyst precursor for copolymerization of ethylene with norbornene.