Rare‐Earth Metal Bis(dimethylsilyl)amide Complexes Supported by Cyclooctatetraenyl Ligands

Monomeric cyclooctatetraenyl rare-earth metal complexes (COT)LnI(thf)3 were examined by X-ray structure analysis for Ln = La and Sm being isostructural to the Nd and Ce congeners. Reaction of the lanthanum derivative with excess AlMe3 led to partial thf displacement and dimerization to [(COT)La(μ-I)(thf)2]2. I–/[N(SiHMe2)2]– salt metathetic ligand exchange involving (COT)LnI(thf)3 (Ln = La, Nd, Sm) and Li[N(SiHMe2)2] did not give putative {(COT)Ln[N(SiHMe2)2](thf)x}. Instead, depending on the metal size, the mixed iodide/amide ate complexes (COT)Ln(μ-I)2{μ-N(SiHMe2)2}Ln(COT)][Li(thf)4] (Ln = Nd, Sm) and (COT)La(μ-I)[μ-N(SiHMe2)2]2La[μ-(η2:η8-COT)]Li(thf)3 were obtained and identified by X-ray structure analyses. In thf solvent, these heteroleptic complexes undergo ligand redistribution to (COT)Ln[μ-(η2:η8-COT)]Li(thf)3, whose solid-state structures were also analyzed by X-ray diffraction (Ln = Nd, Sm). Utilization of K[N(SiHMe2)2] afforded alkali-metal-free (COT)La[N(SiHMe2)2](thf)2 in good yield, whose monomeric composition was determined by X-ray structure analysis.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)