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 [{eta(5)-C(5)Me(4)(SiMe(3))}(2)Ti(eta(2)-Me(3)SiC equivalent to CSiMe(3))] (1) afforded the stable titanocene [(eta(5)-C(5)Me(4)-C(5)Me(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 degrees 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 eta(2)-ethylene complex [(eta(5)-C(5)Me(4)(SiMe(3))}(2)Ti(eta(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 eta(2)-coordinated Me(3)SiC equivalent to CSiMe(3) and CH(2)=CH(2) ligands, respectively.