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

Examples of the ability of the donor-functionalised amide ligands N-(2-methoxyphenyl)-N-(trimethylsilyl)amide (L1) and N-(2phenoxyphenyl)-N-(trimethylsilyl)amide (L2) to support mixed-ligand lanthanoid complexes of the type [Ln(L)2A] or [Ln(L)AB] are described. Reaction of [Yb(OAr)3](Ar = C6H3But2-2,6) with two equivalents of [Li(L^2)]n in hexane gave hexane-soluble, monomeric and five-coordinate [Yb(L2)2(OAr)](1) in high yield. Attempted preparation of an analogous [Yb(L^1)2(MeCp)] complex by reaction of [Yb(MeCp)Cl2(thf)] with [Li(L1)(OEt2)]2(with a Yb : Li ratio of 1 : 2) in thf instead gave the known [Yb(L^1)2((mu)-Cl)]2(2). In contrast, the stable complexes [Yb(MeCp)(L1)((mu)-Cl)]2(3) and [Yb(MeCp)(L^2)((mu)-Cl)]2(4) were readily obtained from 1 : 1 (Li : Yb) reaction of [Yb(MeCp)Cl2(thf)] with [Li(L^1)(OEt2)]2 or [Li(L^2)(dme)] in thf. The complexes 1, 3 and 4 have been characterised by X-ray structure determination.