STERIC CYCLOPENTADIENYL EQUIVALENTS IN F-ELEMENT CHEMISTRY - MONOMERIC, HOMOLEPTIC LANTHANIDE(III) TRIS [N,N'BIS(TRIMETHYLSILYL)BENZAMIDINATES]

Anhydrous lanthanide trichlorides react with N-silylated sodium benzamidinates, Nd[4-RC6H4C(NSiMe3)2], (la - d), to give the monomeric, homoleptic lanthanide(III) benzamidinates [4-RC6H4C(NSiMe3)2]3Ln (2 - 23, R = H, MeO, CF3, Ph). The molecular structure of [4-MeOC6H4C(NSiMe3)2]3Pr (11) has been determined by X-ray diffraction. Absorption and emission measurements reveal that the three benzamidinate ligands produce an unusually large crystal field which is comparable with that of cyclopentadienyl.