Bis[eta(5)-tetramethyl(trimethylsilyl) cyclopentadienyl]titanium(II) and its pi-complexes with bis(trimethylsilyl)acetylene and ethylene

Thermally induced elimination of bis(trimethylsilyl)acetylene from its tita nocene complex [{eta(5)-C5Me4(SiMe3)}(2)Ti(eta(2)-Me3SiC equivalent to CSiM e3)] (1) afforded the stable titanocene [(eta(5)-C5Me4-C5Me3)}(2)Ti-II] (2) in high yield under mild conditions. Compound 2 exhibits paramagnetic line broadening of H-1 NMR signals, although it is silent in EPR spectra down t o -196 degrees C. The solid-state structure determination revealed an exact ly parallel arrangement of the cyclopentadienyl rings in 2 due to crystallo graphically imposed symmetry. Complex 2 smoothly reacts with ethylene to gi ve the yellow eta(2)-ethylene complex [(eta(5)-C5Me4(SiMe3)}(2)Ti(eta(2)-CH 2=CH2)] (3). The structures of 1 and 3, determined by single-crystal X-ray diffraction, show the bent-titanocene moieties with the eta(2)-coordinated Me3SiC equivalent to CSiMe3 and CH2=CH2 ligands, respectively.