Synthesis and X-ray crystal structure of bis[eta(5)-1,3-bis(trimethylsilyl)cyclopentadienyl] lanthanide and yttrium iodide complexes

Treatment of [{(Me3Si)(2)C5H3}2LnCl](2) with excess amounts of NaI in dry THF, or reaction of a mixture of LnCl(3) and NaI with two equivalents of [(Me3Si)(2)C5H3]Na in dry THF at room temperature, gave five new monomeric complexes [(Me3Si)(2)C5H3](2)LnI(THF) (Ln = La (1), Sm (2), Y (3), Er (4), Lu (5)) in 50-69% yield. The mixed pi-ligand complex [{(Me3Si)(2)C5H3}{(Me3Si)C5H4}]LnI(THF) (6) was also prepared in a similar manner. The compounds were fully characterized by elemental analyses, IR and MS spectroscopy, H-1 NMR (for diamagnetic metals) and single-crystal X-ray diffraction studies (except 1). In each compound, the C-5 ring centroids, the THF oxygen atom and iodide ligand describe a distorted tetrahedral geometry around the metal. The variations in the metal-iodide bond distances are not as predictable as those in metal-carbon and metal-oxygen bond distances. (C) 1997 Elsevier Science S.A.