Synthesis of trichloro(η5-alkenyltetramethyl- cyclopentadienyl)titanium(IV) complexes and their activity in styrene polymerization

Fully substituted trichloro(eta (5)-cyclopentadienyl)titanium(IV) complexes with pendant alkenyl groups, [TiCl3(eta (5)-C5Me4R)] (R = CH(Me)CH=CH2 (3a), (CH2)(2)CH=CH2 (3b), and (CH2)(3)CH=CH2 (3c)), were synthesized by the reaction of the corresponding trimethylsilyl or trimethylstannyl substituted cyclopentadienes C5Me4R(EMe3), where E = Si or Sn, with TiCl4. In all cases, the pendant double bonds did not exhibit any interaction with the titanium atoms as indicated by H-1, C-13 NMR or IR spectra as well as by the solid-state structure of 3c. The catalytic systems prepared by mixing complexes 3a-3c, [TiCl3(eta (5)-C5Me5)], [TiCl3(eta (5)-C5H5)], and similar complexes with R = butyl (4), phenyl (5), 4-fluorophenyl (6) with methylalumoxane (MAO) at the molar ratio Al/Ti = 500 catalyzed polymerization of Styrene to syndiotactic polystyrene. Their polymerization activities increase in the order: [TiCl3(eta (5)-C5Me5)] < 3a < 3b < 3c < 4 < 5 < 6 < [TiCl3(eta (5)-C5H5)], while the molecular weights (M-W) of syndiotactic polystyrene grow in the order: [TiCl3(eta (5)-C5H5)] < 3a < 3b < 4 approximate to 6 < [TiCl3(eta (5)-C5Me5)] < 3c approximate to 5 (maximum M-W ca 3.0 . 10(5)). A comparison of the results for the catalytic systems based on 4 with those derived from 3a-3c points to a rather weak competition of the pendant double bonds with monomer for a cationic Ti(III) catalytic centre.