Collect. Czech. Chem. Commun. 2011, 76, 75-94
Published online 2011-01-06 09:12:25

Titanocene and ansa-titanocene complexes bearing 2,6-bis(isopropyl)phenoxide ligand(s). Syntheses, characterization and use in catalytic dehydrocoupling polymerization of phenylsilane

Michal Horáčeka, Jan Mernab, Róbert Gyepesc, Jan Sýkorad, Jiří Kubištaa and Jiří Pinkasa,*

a J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, v.v.i., Dolejškova 2155/3, 182 23 Prague 8, Czech Republic
b Institute of Chemical Technology, Prague, Department of Polymers, Technická 5, 166 28 Prague 6, Czech Republic
c Charles University, Department of Inorganic Chemistry, Hlavova 2030, 128 43 Prague 2, Czech Republic
d Institute of Chemical Process Fundamentals, Academy of Sciences of the Czech Republic, v.v.i., Rozvojová 135, 165 02 Prague 6, Czech Republic


Aryloxychloro and bis(aryloxy) titanocenes of general formula L2TiCl2–x(OAr′)x where L = η5-C5H5 (x = 1 (1) and 2 (2)), L2 = SiMe25-C5H4)2 (x = 1 (3) and 2 (4)), and Ar′ = 2,6-(CHMe2)2C6H3 were prepared by the reaction of corresponding titanocene dichloride with LiOAr′ and characterized by spectroscopic methods and compound 3 by single crystal X-ray diffraction analysis. The bulky aryloxy ligand in 1 and 3 exerts a hindered rotation around the Ti–O bond on the 1H NMR time scale, resulting in its dynamic behavior in CDCl3 solution. Variable temperature NMR measurements proved the rotation barrier in 3G298 = 13.9 ± 0.3 kcal/mol) to be lower than that in 1G298 = 14.7 ± 0.2 kcal/mol) as a consequence of the more open titanocene shell in the ansa-structure of 3. The catalytic behavior of complexes 14, [(η5-C5H5)2TiCl2] and [{SiMe25-C5H4)2}TiCl2], was examined in dehydrocoupling polymerization of phenylsilane under comparable conditions, showing a remarkable higher activity for the titanocene complexes with regards to the ansa-titanocene ones. The order of catalytic activities 2 ~ 1 > [(η5-C5H5)2TiCl2] >> [{SiMe25-C5H4)2}TiCl2] ~ 3 ~ 4 reveals the aryloxy ligands to have an enhancing effect on activity in the titanocene series.

Keywords: Titanium; Metallocenes; Polymerizations; Silicon; Titanocene complexes; Dehydrocoupling; Polysilanes; Dynamic NMR spectroscopy; X-Ray diffraction.

References: 50 live references.