Lithium and lanthanoid(III) complexes of the chelating N,N-dimethyl-N′-trimethylsilylethane-1,2-diaminate(1–) ligand

Abstract

Deprotonation of N,N-dimethyl-N′-trimethylsilylethane-1,2-diamine (HL¹) with LiBuⁿ in hexane yielded solvent-free LiL¹, whilst in diethyl ether the dinuclear complex [LiL¹₂Li(OEt₂)] was obtained. A single-crystal structure determination of the etherate showed one four-co-ordinate Li atom bound to two chelating amide ligands which were further bound, through the amide nitrogens, to a three-co-ordinate lithium centre which also has a co-ordinated diethyl ether molecule. The complex [{LiL¹LiClLiL¹(thf)}₂] (thf = tetrahydrofuran) was formed as a side product of a reaction of [LiL¹(thf)_n] with [LuCl₃(thf)₂] in thf. In the solid state the structure shows a LiCl bonded between LiL¹ and LiL¹(thf) units generating a ‘three-rung ladder’, which is further connected, by Li–Cl bonds, to a second LiL¹LiClLiL¹(thf) moiety. The dimer has two rare Li₄Cl units. Three equivalents of [LiL¹(thf)_n], prepared in situ in thf, reacted with [LuCl₃(thf)₂], anhydrous LnCl₃ (Ln = Er, Eu, Sm or Nd) or [LaBr₃(thf)₃] to form the hexane-soluble [LnL¹₃]. Monomeric six-co-ordinate, distorted-octahedral complexes with three chelating L¹ ligands in a fac orientation were found for Ln = Lu, Er or Eu by single-crystal X-ray studies. Reaction of 2 equivalents of LiL¹ with ErCl₃ in thf generated heteroleptic [ErL¹₂Cl].