Ln(II)/Pb(II)–Ln(III)/Pb(0) Redox Approach toward Rare-Earth-Metal Half-Sandwich Complexes
作者:André M. Bienfait、Benjamin M. Wolf、Karl W. Törnroos、Reiner Anwander
DOI:10.1021/acs.organomet.5b00837
日期:2015.12.28
The divalent bis(trimethylsilyl)amide complexes Ln[N(SiMe3)(2)](2)(THF)(2) (Ln = Sm, Yb) react with 0.5 equiv of lead(II) pentamethylcydopentadienide, Cp-2*Pb (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(SiMes)(2)](2)(THF)(2) resulted in the cocrystallization of the sandwich complex Cp-2*Eu[N(SiMe3)(2)] and homoleptic Eu[N(SiMe3)(2)](3). The divalent bis(dimethylsilyl)amide complexes Lnmu-N(SiHMe2)(2)}(2)Ln[N(SiHMe2)(2)](THF)}(2) (Ln = Sm, Yb) react with 1.5 equiv of Cp-2*Pb 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 (Hpz(tBu,Me)) in THF generates [(pz(tBu,Me))Eu(mu-pz(tBu,Me))(THF)(2)](2). Oxidation of the europium(II) pyrazolate complex with 1 equiv of Cp-2*Pb in THF afforded Cp*Eu(mu-pz(tBu,Me)) (THF)(2). The tetramethylaluminate compounds Ln(AlMe4)(2)}(n) (Ln = Sm, Yb) react with 0.5 equiv of PbCp2* in n-hexane to produce mixtures of half-sandwich and metallocene complexes Cp*Ln(AlMe4)(2) and [Cp-2*Ln(mu-AlMe4)](2), respectively. The attempted oxidation of Eu(AlMe4)(2)} led to the formation of Cp*Eu(AlMe4)}, which could be crystallized from THF to give polymeric Cp*Eu(mu-AlMe4)(THF)(3)}(n). The reaction of "chloro-contaminated" Sm(AlMe4)(2)} with 2 equiv of HCp* performed in THF led to the isolation of the unexpected mixed chloride methylidene complex [Cp-3*Sm-3(mu(2)-Cl)(3)(mu(3)-Cl)(mu(3)-CH2)(THF)(3)]. Reacting Yb(AlEt4)(2)}(n) with 0.5 equiv of Cp-2*Pb in n-hexane gave a mixture of products, from which Cp-2*Yb(AlEt4) was identified. Performing the same reaction in toluene in the presence of diethyl ether resulted in the formation of the divalent metathesis product Cp*Yb(AlEt4)(Et2O)(2).