Mixed-ligand ytterbium(III) complexes incorporating one or two bidentate (N,O) amide ligands

摘要

Examples of the ability of the donor-functionalised amide ligands N-(2-methoxyphenyl)-N-(trimethylsilyl)amide (L~1) and N-(2-phenoxyphenyl)-N-(trimethylsilyl)amide (L~2) to support mixed-ligand lanthanoid complexes of the type [Ln(L)_2A] or [Ln(L)AB] are described. Reaction of [Yb(OAr)_3] (Ar = C_6H_3Bu_2~t-2,6) with two equivalents of [Li(L~2)]_n in hexane gave hexane-soluble, monomeric and five-coordinate [Yb(L~2)_2(OAr)] (1) in high yield. Attempted preparation of an analogous [Yb(L~1)_2(MeCp)] complex by reaction of [Yb(MeCp)Cl_2(thf)] with [Li(L~1)(OEt_2)]_2 (with a Yb:Li ratio of 1:2) in thf instead gave the known [Yb(L~1)_2(μ-Cl)]_2 (2). In contrast, the stable complexes [Yb(MeCp)(L~1)(μ-Cl)]_2 (3) and [Yb(MeCp)(L~2)(μ-Cl)]_2 (4) were readily obtained from 1:1 (Li:Yb) reaction of [Yb(MeCp)Cl_2(thf)] with [Li(L~1)(OEt_2)]_2 or [Li(L~2)(dme)] in thf. The complexes 1, 3 and have been characterised by X-ray structure determination.