Divalent europium and ytterbium complexes supported by a bulky 2-pyridyl amido ligand: synthesis, structure and reactivity studies

Abstract

Metallation of the N-arylated 2-pyridyl amine [HN(C₆H₃Prⁱ₂-2,6)(2-C₅H₃N-6-Me)] (1) with potassium hydride in Et₂O and THF yielded potassium amides [{KL(OEt₂)}₂] [L = N(C₆H₃Prⁱ₂-2,6)(2-C₅H₃N-6-Me)] (2) and KL(THF)₂ (3), respectively. Treatment of LnI₂(THF)₂ (Ln = Eu, Yb) with 2 afforded the corresponding Ln(II) amido complexes [EuL(μ-L)₂K(THF)] (4) and [YbL₂(THF)₂] (5). In contrast, an analogous reaction of SmI₂(THF)₂ with 2 only led to the isolation of homoleptic Sm(III) triamide [SmL₃] (6). The reaction chemistry of divalent complexes 4 and 5 was examined. Oxidation of the Eu(II) amido complex 4 by iodine yielded the trivalent [EuL₃] (7), whereas addition of Yb(II) diamide 5 to iodine led to the isolation of the bis(amido) Yb(III) iodide complex [YbL₂(I)(THF)] (8). Complex 8 could also be prepared by the reaction of 5 with copper(I) iodide. A subsequent reaction of 8 with KOBu^t gave, unexpectedly, the Yb(III) triamide [YbL₃] (9). Reactions of complex 5 with diphenyl dichalcogenides PhEEPh (E = S, Se, Te) also gave [YbL₃] (9) as the only isolable product. The solid-state structures of complexes 2 and 4–9 were elucidated by X-ray diffraction analysis.