SYNTHESES AND CRYSTAL-STRUCTURES OF IMETHYLSILYL)-TETRAMETHYLCYCLOPENTADIENYL]TITANIUM DICHLORIDE AND MONOCHLORIDE

(Trimethylsilyl)tetramethylcyclopentadiene (Cp'H) was obtained from th e lithium salt of tetramethylcyclopentadiene and trimethylsilyl chlori de. rimethylsilyl)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 bu lky trimethylsilyl groups in side positions on opposite sides of the C E-Ti-CE planes. The steric congestion between the two chlorine atoms a nd two trimethylsilyl groups in 1 resulted in the nearly eclipsed conf ormation of the rings. Consequently, the steric hindrance between the methyl groups at the hinge position of the Cp' ligands led to a decrea se in the angle between the Cp' ring planes by 4.8 degrees, compared w ith the value of 44.6 degrees in (C(5)Me(5))(2)TiCl2. The titanocene s keleton in 2 is virtually the same as in (C(5)Me(5))(2)TiCl. The elect ronic effect of the trimethylsilyl group upon various properties of 1 and 2 appeared to be ambiguous. Based on the position of lambda(max) o f 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 trimeth ylsilyl group close to that of hydrogen and the anisotropy of the EPR g-tensor of 2 close to that of the methyl group.