Abstrakt
Solutions of permethylcyclopentadienyl-tethered titanium(IV) chlorides incorporating one double bond in their tethers were exposed in glass vessels to sunlight, which triggered their photolytical reactions providing mixtures of products. Although the formation of several different products was apparent from H-1 NMR spectra, only a single product could be identified in the crude reaction mixtures.
This product was dicyclopentadiene [C10Me10], which arose from the recombination of the generally photodissociated C5Me5 radical. Amongst products that contained titanium, three complexes (3a, 3b and 4a) could be isolated after employing fractional crystallization and these complexes were characterized.
The mechanism of 3a formation involves photodissociation of one η(5)-C5Me5 ligand from the parent complex, complemented by chlorine abstraction from another reactant molecule. Complexes 3b and 4a become formed via tether rearrangement, which starts with dissociating the tether Ti-C bond and is followed by rotating the tether, reattaching it subsequently through its available radical terminus.