EXO,EXO-BIS(ISODICYCLOPENTADIENYL)TITANIUM AND EXO,EXO-BIS(ISODICYCLOPENTADIENYL)ZIRCONIUM DICHLORIDES - CONFORMATIONAL CHARACTERIZATION OFTHE HOMOGENEOUS ZIEGLER CATALYST PRECURSORS IN SOLUTION

exo,exo-Bis(isodicyclopentadienyl)titanium dichloride (1) exhibits a c hiral C-2-symmetric structure in solution that is characterized by a b is-lateral:anti orientation of the annulated bicyclo[2.2.1]heptene moi eties at the bent-metallocene wedge. This was shown by dynamic NMR spe ctroscopy of complex 1 in [D-2]dichloromethane solution. The activatio n energy for the conformational inversion of complex 1 is Delta G doub le dagger (rot)(198 K) = 9.8 +/- 0.4 kcal mol(-1). The bent-metallocen e rotational barrier of the analogous zirconium complex (2) is much lo wer (similar to 6 kcal mol(-1)). Complexes 1 and 2 were both used to g enerate active homogeneous Ziegler catalyst systems for alpha-olefin p olymerization.