Treatment of 2, 5-hexandione with cyclopentadiene in the presence of pyrrolidine yields the corresponding bisfulvene (5) that has been converted to the [4-cyclopentadienyliden-4, 7, 7- trimethyl-4, 5, 6, 7-tetrahydroindenyl] lignad system, isolated as the dilithio compound 8. Subsequent reaction with the group 4 metal halides MCl4 (M= Ti, Zr, Hf) gives the rigid ansametallocene dichlorides 9a-c. Their reaction with methyllithium yields the ...
