Synthetic Aspects of (C5H4SiMe3)3Ln Rare-Earth Chemistry: Formation of (C5H4SiMe3)3Lu via [(C5H4SiMe3)2Ln]+ Metallocene Precursors

New analogues of Cp′3Ln (Cp′ = C5H4SiMe3, Ln = rare earth) complexes have been synthesized with the largest and smallest lanthanides, La and Lu. Due to the smaller size of Lu, the reaction of LuCl3 with 3 equiv of KCp′ produced only traces of Cp′3Lu, yielding [Cp′2Lu(μ-Cl)]2 as the major product. An alternative route was developed in which [Cp′2Lu(μ-Cl)]2 reacts with (C3H5)MgCl to form the tetrameric allyl complex [Cp′2Lu(μ-η1:η1-C3H5)]4. The allyl complex reacts with [HNEt3][BPh4] to generate [Cp′2Lu(THF)2][BPh4], which reacts with KCp′ to produce Cp′3Lu in good yield. The reaction of LaCl3 with 3 equiv of KCp′ in Et2O gave the unsolvated Cp′3La, while the same reaction in rigorously dry THF gave solvated Cp′3La(THF). The reaction of LaCl3 and KCp′ in improperly dried THF gave the mixed-ligand complex Cp′2CpLa(THF) (Cp = C5H5), rather than the expected hydrolysis product, [Cp′2La(μ-OH)]2.