Bis[η5-tetramethyl(trimethylsilyl)cyclopentadienyl]titanium(II) and Its π-Complexes with Bis(trimethylsilyl)acetylene and Ethylene

Thermally induced elimination of bis(trimethylsilyl)acetylene from its titanocene complex [{η 5 -C 5 Me 4 (SiMe 3 )} 2 Ti(η 2 -Me 3 SiC⋮CSiMe 3 )] ( 1 ) afforded the stable titanocene [{η 5 -C 5 Me 4 (SiMe 3 )} 2 Ti II ] ( 2 ) in high yield under mild conditions. Compound 2 exhibits paramagnetic line broadening of 1 H 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 η 2 -ethylene complex [{η 5 -C 5 Me 4 (SiMe 3 )} 2 Ti(η 2 -CH 2 CH 2 )] ( 3 ). The structures of 1 and 3, determined by single-crystal X-ray diffraction, show the bent-titanocene moieties with the η 2 -coordinated Me 3 SiC⋮CSiMe 3 and CH 2 CH 2 ligands, respectively.