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

Monomeric c yclo o cta t etraenyl 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 AlMe 3 led to partial thf displacement and dimerization to [(COT)La(μ‐I)(thf) 2 ] 2 . I – /[N(SiHMe 2 ) 2 ] – salt metathetic ligand exchange involving (COT)LnI(thf) 3 (Ln = La, Nd, Sm) and Li[N(SiHMe 2 ) 2 ] did not give putative {(COT)Ln[N(SiHMe 2 ) 2 ](thf) x }. Instead, depending on the metal size, the mixed iodide/amide ate complexes (COT)Ln(μ‐I) 2 {μ‐N(SiHMe 2 ) 2 }Ln(COT)][Li(thf) 4 ] (Ln = Nd, Sm) and (COT)La(μ‐I)[μ‐N(SiHMe 2 ) 2 ] 2 La[μ‐(η 2 :η 8 ‐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‐(η 2 :η 8 ‐COT)]Li(thf) 3 , whose solid‐state structures were also analyzed by X‐ray diffraction (Ln = Nd, Sm). Utilization of K[N(SiHMe 2 ) 2 ] afforded alkali‐metal‐free (COT)La[N(SiHMe 2 ) 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)