Dimethyl titanocene Y: a valuable precursor for libraries of cytotoxic titanocene derivatives.

Reaction of the known titanocene Y 2 with methyl lithium at -15 degrees C yields bis-[(p-methoxybenzyl)cyclopentadienyl]titanium(IV) dimethyl (dimethyl titanocene Y, 3), a hitherto unknown, surprisingly robust titanium (IV) dimethyl species. Dimethyl titanocene Y was utilized in the preparation of several bis-[(p-methoxybenzyl)cyclopentadienyl]titanium(IV) dicarboxylates by the reaction with the free carboxylic acids in fair to good yields. Cytotoxicity of all new compounds has been estimated in Hela S3 cells.