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

Metallation of the N-arylated 2-pyridyl amine [HN(C6H3Pr(i)2-2,6)(2-C5H3N-6-Me)] (1) with potassium hydride in Et2O and THF yielded potassium amides [{KL(OEt2)}2] [L = N(C6H3Pr(i)2-2,6)(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 KOBut 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.