Collect. Czech. Chem. Commun. 2001, 66, 1359-1374

Synthesis of Trichloro(η5-alkenyltetramethylcyclopentadienyl)titanium(IV) Complexes and Their Activity in Styrene Polymerization

Jaroslav Zemáneka, Lenka Fröhlichováb, Pavel Šindelářb, Petr Štěpničkac, Ivana Císařovác, Vojtech Vargad, Michal Horáčeka and Karel Macha,*

a J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, Dolejškova 3, 182 23 Prague 8, Czech Republic
b Polymer Institute Brno, 656 49 Brno, Czech Republic
c Department of Inorganic Chemistry, Charles University, 128 40 Prague 2, Czech Republic
d Research Institute of Inorganic Chemistry, 400 01 Ústí nad Labem, Czech Republic


Fully substituted trichloro(η5-cyclopentadienyl)titanium(IV) complexes with pendant alkenyl groups, [TiCl35-C5Me4R)] (R = CH(Me)CH=CH2 (3a), (CH2)2CH=CH2 (3b), and (CH2)3CH=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 1H, 13C NMR or IR spectra as well as by the solid-state structure of 3c. The catalytic systems prepared by mixing complexes 3a-3c, [TiCl35-C5Me5)], [TiCl35-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: [TiCl35-C5Me5)] < 3a < 3b < 3c < 4 < 5 < 6 < [TiCl35-C5H5)], while the molecular weights (Mw) of syndiotactic polystyrene grow in the order: [TiCl35-C5H5)] < 3a <3b < 46 < [TiCl35-C5Me5)] < 3c5 (maximum Mw ca 3.0 · 105). 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.

Keywords: Titanium; Half-sandwich complexes; Trichloro(cyclopentadienyl)titanium complexes; Substituted cyclopentadienyl ligands; Pendant alkenyl groups; Crystal structure; Styrene; Cationic polymerizations; Syndiotactic polystyrene.

References: 35 live references.