tert-Butyl(cyclopentadienyl) Ligands Will Stabilize Nontraditional +2 Rare-Earth Metal Ions

Reduction of the tris­(tert-butylcyclopentadienyl) complexes, Cpt3Ln (Cpt = C5H4CMe3), with potassium in the presence of 18-crown-6 forms the crystallographically characterizable Ln­(II) complexes, {[K­(18-crown-6)]­[(μ-Cpt)2CeCpt]}n and [K­(18-crown-6)­(THF)2]­[Cpt3Ln] (Ln = Ce, Gd). EPR data indicate that La­(II) and Y­(II) complexes also form upon reduction of Cpt3Ln. Single crystals of the mixed-valent complexes, [K­(18-crown-6)]­[(μ-Cpt)­CeCpt2]2 and [K­(2.2.2-cryptand)]­[Cpt3Dy]2, have also been isolated as part of this study and structurally characterized.