Ln(II)/Pb(II)–Ln(III)/Pb(0) Redox Approach toward Rare-Earth-Metal Half-Sandwich Complexes

Abstract

The divalent bis(trimethylsilyl)amide complexes Ln[N(SiMe3)2]2(THF)2 (Ln = Sm, Yb) react with 0.5 equiv of lead(II) pentamethylcyclopentadienide, Cp*2Pb (Cp* = C5Me5), in n-hexane to form the half-sandwich complexes Cp*Ln[N(SiMe3)2]2 (Ln = Sm, Yb) in almost quantitative yield. The same reaction performed with Eu[N(SiMe3)2]2(THF)2 resulted in the cocrystallization of the sandwich complex Cp*2Eu[N(SiMe3)2] and homoleptic Eu[N(SiMe3)2]3. The divalent bis(dimethylsilyl)amide complexes Ln{[μ-N(SiHMe2)2]2Ln[N(SiHMe2)2](THF)}2 (Ln = Sm, Yb) react with 1.5 equiv of Cp*2Pb in n-hexane/THF to form the half-sandwich complexes Cp*Ln[N(SiHMe2)2]2(THF) (Ln = Sm, Yb). The corresponding europium reaction did not provide any crystalline material. Treatment of divalent Eu[N(SiMe3)2]2(THF)2 with 2 equiv of 3-tert-butyl-5-methylpyrazole (HpztBu,Me) in THF generates [(pztBu,Me)Eu(μ-pztBu,Me)(THF)2]2. Oxidation of the europium(II) pyrazolate complex with 1 equiv of Cp*2Pb in THF afforded Cp*Eu(μ-pztBu,Me)2(THF)2. The tetrameth...