SYNTHESES AND CRYSTAL-STRUCTURES OF (ETA-5-C5H5)3LN(THF) (LN=CE, ER)

Brown crystalline tricyclopentadienyl cerium tetrahydrofuranate (THF) complex (eta5-C5H5)3Ce(THF) was prepared by the reaction of (NH4)2Ce(N O3)6 with sodium cyclopentadienide (C5H5Na) in THF at molar ratio of 1 :6. ErCl3.4THF reacts with potassium cyclooctadienide (C8H11K) at - 78 -degrees-C and then with C5H5Na at room temperature in THF at a molar ratio of 1:1:2 to give pink crystals of (eta5-C5H5),Er(THF). The cryst al structure determination of both these complexes shows that both bel ong to monoclinic space group P2(1)/n, but their structures differ in that the Ce complex is not isostructural with (eta'-C5H5)3Ln(THF) (Ln = La, Pr, Nd, Gd, Dy, Y and Lu). However, the Er complex structure is isostructural. There are two discontinuity points at Ce and Dy but no ''gadolinium break phenomenon'' in the regularity of lanthanide contra ction.