Syntheses and structures of mono‐cyclopentadienyl di‐iodide complexes of the lanthanides: X‐ray crystal structures of Cp‴LaI2py3 (Cp‴ = [η5‐C5H2(SiMe3)3‐1,2,4]−; py = pyridine) and Cp‴LaI2(bipy)py (bipy = 2, 2′‐bipyridine)

Abstract

Abstract[η5‐C5H2(SiMe3)3‐1,2,4]K reacts with LaI3(THF)4 in tetrahydrofuran (THF) to form the mono‐ring complex [η5‐C5H2(SiMe3)3‐1,2,4]LaI2(THF)x (1). Elemental analysis and 1H NMR spectroscopy indicate that the coordinated THF molecules are labile and are easily removed under vacuum. The THF adduct 1 is readily converted to the more stable pyridine complex [η5‐C5H2(SiMe3)3‐1,2,4]LaI2py3 (2) by the addition of excess pyridine to a toluene solution of 1. Although solid samples of 2 lose pyridine less readily, the pyridine molecules exchange with solvent molecules, and in the presence of a large excess of THF, 1 is re‐formed. Complex 2 may be crystallized from toluene, and an X‐ray diffraction study revealed a monomeric species with the two iodide ligands trans to each other, and three pyridines arranged in a meridional fashion. The addition of one equivalent of 2,2′‐bipyridine to a toluene solution of 1 yields the bipyridine adduct, [η5‐C5H2(SiMe3)3‐1,2,4]LaI2(bipy) (3). In contrast to 1 and 2, the bipyridine molecule in 3 remains ligated to the lanthanum center in all solvents. Complex 3·py may be crystallized from THF–pyridine; in this case, the presence of bipyridine forces a cis orientation of the two iodide ligands. Copyright © 2003 John Wiley & Sons, Ltd.