Collect. Czech. Chem. Commun. 1996, 61, 1307-1320

Syntheses and Crystal Structures of Bis[(trimethylsilyl)tetramethylcyclopentadienyl]titanium Dichloride and Monochloride

Michal Horáčeka, Róbert Gyepesb, Ivana Císařováb, Miroslav Polášeka, Vojtech Vargaa and Karel Macha

a J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, 182 23 Prague 8, Czech Republic
b Department of Inorganic Chemistry, Charles University, 128 40 Prague 2, Czech Republic


(Trimethylsilyl)tetramethylcyclopentadiene (Cp'H) was obtained from the lithium salt of tetramethylcyclopentadiene and trimethylsilyl chloride. Bis[(trimethylsilyl)tetramethylcyclopentadienyl]titanium dichloride (1) and monochloride (2) were prepared by the generally known procedures. The X-ray crystal structures of 1 and 2 showed the placement of the bulky trimethylsilyl groups in side positions on opposite sides of the CE-Ti-CE planes. The steric congestion between the two chlorine atoms and two trimethylsilyl groups in 1 resulted in the nearly eclipsed conformation of the rings. Consequently, the steric hindrance between the methyl groups at the hinge position of the Cp' ligands led to a decrease in the angle between the Cp' ring planes by 4.8°, compared with the value of 44.6° in (C5Me5)2TiCl2. The titanocene skeleton in 2 is virtually the same as in (C5Me5)2TiCl. The electronic effect of the trimethylsilyl group upon various properties of 1 and 2 appeared to be ambiguous. Based on the position of λmax of electronic absorption bands of 1 the trimethylsilyl group exerted a stronger electron donation effect than the methyl group, however, the affinity of 2 to 2-methyltetrahydrofuran put the effect of the trimethylsilyl group close to that of hydrogen and the anisotropy of the EPR g-tensor of 2 close to that of the methyl group.

Keywords: Titanium; Titanocene chlorides; (Trimethylsilyl)tetramethylcyclopentadienyl ligand; Crystal structures; Electronic effects of trimethylsilyl group.