SYNTHESIS OF LANTHANIDE COMPLEXES COORDINATED BY AN ASYMMETRIC CYCLOPENTADIENYL LIGAND

The synthesis and characterization of bis- and monocyclopentadienyl la nthanide iodides [(S)-Cp'](2)LnI (Ln = Sm, 3; Ln = La, 4) and (S)-Cp'L nI(2)(THF)(n), (Ln = Sm, n = 3, 5; Ln = La, n = 2, 6) coordinated by a n asymmetric cyclopentadienyl ligand (Cp' = C5H4CH2CH(CH3)OCH(2)Ph) ha ve been carried out. Variable-temperature NMR study of compounds 3 and 4 reveals a fluxional process in solution. The X-ray crystal structur e analysis of 3 shows a bent metallocene structure with intramolecular coordination to the oxygen atoms of the side chains of both cyclopent adienyl ligands. For monocyclopentadienyl complexes, intramolecular co ordination is observed only for the lanthanum complex 6. All compounds exhibit activity for the catalysis of Diels-Alder reactions.