Synthesis of heteroleptic yttrium and dysprosium 1,2,4-tris(trimethylsilyl)cyclopentadienyl complexes

We report the synthesis of heteroleptic dysprosium complexes of the 1,2,4-tris(trimethylsilyl)cyclopentadienyl ligand (Cp‴={C5H2(SiMe3)3-1,2,4}), and diamagnetic yttrium analogues, by salt metathesis protocols from KCp‴ and molecular lanthanoid halide or borohydride precursors: [{Ln(Cp‴)2(μ-Cl)2K}2]∞ (1-Ln; Ln = Y, Dy), [Ln(Cp‴)2(THF)(Cl)] (2-Ln; Ln = Y, Dy), [Y(Cp‴)2(η3-C3H5)] (3-Y), [Y(Cp‴)(BH4)2(THF)] (4-Y), [Dy(Cp‴)(BH4)(μ-BH4)]4 (5-Dy) and [Ln(Cp‴)2(BH4)] (6-Ln; Ln = Y, Dy); several crystals of [Dy(Cp‴)2(BH4)(THF)] (7-Dy) formed on one occasion during the isolation of 6-Dy. Efforts to prepare the isolated lanthanoid metallocenium cations [Ln(Cp‴)2]+ for Y and Dy were not successful by the anion abstraction methods investigated herein; however, several crystals of the contact ion-pair complex [Y(Cp‴)2{(μ-Ph)2BPh2}] (8-Y) formed from the reaction of 3-Y with [NEt3H][BPh4]. On one occasion during the preparation of 3-Y we isolated several crystals of [Mg(Cp‴)(THF)(μ-Cl)]2. Complexes 1-6 and [NEt3H][BPh4] were all structurally authenticated by single crystal XRD and characterised by IR spectroscopy and elemental analysis, with magnetic susceptibility for dysprosium complexes determined by the Evans method, and yttrium analogues studied by multinuclear NMR spectroscopy; complexes 7-Dy, 8-Y, and [Mg(Cp‴)(THF)(μ-Cl)]2 were characterised by single crystal XRD only. The magnetic properties of 5-Dy were probed by SQUID magnetometry and ab initio calculations.