Thermally induced elimination of bis(trimethylsilyl)acetylene from its titanocene complex [{η5-C5Me4(SiMe3)}2Ti(η2-Me3SiC⋮CSiMe3)] (1) afforded the stable titanocene [{η5-C5Me4(SiMe3)}2TiII] (2) in high yield under mild conditions. Compound 2 exhibits paramagnetic line broadening of 1H NMR signals, although it is silent in EPR spectra down to −196 °C. The solid-state structure determination revealed an exactly parallel arrangement of the cyclopentadienyl rings in 2 due to crystallographically imposed symmetry. Complex 2 smoothly reacts with ethylene to give the yellow η2-ethylene complex [{η5-C5Me4(SiMe3)}2Ti(η2-CH2CH2)] (3). The structures of 1 and 3, determined by single-crystal X-ray diffraction, show the bent-titanocene moieties with the η2-coordinated Me3SiC⋮CSiMe3 and CH2CH2 ligands, respectively.

Dichlorobis[η5-tetramethyl(phenyl)cyclopentadienyl]titanium(IV) (1) and chlorobis[η5-tetramethyl- (phenyl)cyclopentadienyl]titanium(III) (2) were prepared by the generally known procedures. The X-ray crystal structures of 1 and 2 showed nearly identical Ti-CE (CE - centroid of the cyclopentadienyl ring) and Ti-Cl distances, the CE-Ti-CE angles and dihedral angles between least-squares planes of the cyclopentadienyl rings to those in [(C5Me5)2TiCl2] and [(C5Me5)2TiCl], respectively. ESR spectra of 2 in 2-methyltetrahydrofuran (MTHF) solutions and glasses revealed that 2 coordinates MTHF to give [(C5Me4Ph)2Ti(Cl)(MTHF)] (2a). The formation of 2a in MTHF solution is completed by lowering temperature to 205 K. A comparison with the known data gives the following order of affinity of [(C5Me4R)2TiCl] towards MTHF: Ph > SiMe3 > H > Me.