Re-investigation of ortho-metalated N,N-dialkylbenzylamine complexes of rare-earth metals. First structurally characterized arylates of neodymium and gadolinium Li[LnAr4]

The influence of the ether ligand in [LnCl3(solv)n], solv = THF, DME; n = 1–3 in reactions with ortho-lithiated dimethyl-benzylamine Li(dmba) has been studied. An improved protocol towards homoleptic tris-aryl complexes of the type [Ln(dmba)3], Ln = Y, Er and Yb has been developed and molecular structures of these complexes have been established by X-ray crystallography. For the first time stable homoleptic lithium ate-complexes of the type Li[Ln(dmba)4] (Ln = Gd, Nd) have been isolated and structurally characterized. The success in their synthesis strongly depends on the choice of the appropriate [LnCl3(solv)n] precursor, such as [GdCl3(dme)2], [NdCl3(dme)], and THF-free reaction conditions. Factors influencing on possible degradation pathways of lanthanide tris-aryl complexes with dmba-type ligands are discussed.