Heteroleptic lanthanide(III) complexes: synthetic utility and versatility of the unsubstituted bis-scorpionate ligand framework

Abstract

The unsubstituted bis-hydrotris(1-pyrazolyl)borate) (Tp) ligand framework has been used to synthesise a range of heteroleptic Ln(III) coordination complexes [Ln(Tp)2(X)]. The precursor complexes [Ln(Tp)2(OTf)] 1-Ln (Ln = Y, Eu, Gd, Yb; OTf = triflate) were synthesised by reaction of Ln(OTf)3 with two equivalents of K(Tp). The 8-coordinate β-diketonate complexes [Ln(Tp)2(hfac)] 2-Ln (Ln = Y, Eu, Yb; hfac = hexafluoroacetylacetonate) were synthesised from Ln(OTf)3 by reacting 1-Ln generated in situ with an equivalent of K(hfac). The 7-coordinate amide complexes [Ln(Tp)2(N″)] 3-Ln (Ln = Y, Yb; N″ = bis(trimethylsilyl)amide) were synthesised from 1-Ln by reaction with K(N″). Reactivity of 3-Ln towards protonolysis was demonstrated by the isolation of the hydroxide dimer [{Y(Tp)2(μ-OH)}2] 4-Y from adventitious reaction with water and the aryloxide complex [Ln(Tp)2(OAr)] 5-Ln (Ln = Y, Yb; OAr = 2,6-tBu2-4-Me-phenoxide) from reaction with H(OAr). Full characterisation data are presented for all complexes, including solid-state molecular structure determination by single-crystal X-ray diffraction.