Anionic dichlorolanthanocene compounds. X-ray crystal structures of [{(Me3Si)2C5H3}2LnCl2][Li(THF)4] (Ln=Er, Yb) and {(Me3Si)2C5H3}2Yb(μ-Cl)2Li(THF)2

Treatment of LnCl3 with two equivalents of Cp″Li (Cp″=(Me3Si)2C5H3) in THF gave, after crystallization from a THF–n-hexane solution at −30°C, ionic compounds [Cp″2LnCl2][Li(THF)4] (Ln=Er (1), Yb (2)) in good yield. Recrystallization of 2 from a toluene solution afforded an ‘ate’ compound Cp″2Yb(μ-Cl)2Li(THF)2 (3). Interestingly, recrystallization of 3 from a mixed solvent of THF–n-hexane did not give compound 2, and only 3 was isolated, indicating that the dissociation of THF may be an irreversible process or 3 is a thermodynamically more stable compound. All three compounds were fully characterized by various spectroscopic date and single-crystal X-ray analyses. Compounds 1 and 2 are the rare structurally characterized examples of an anionic dichlorolanthanocene stabilized by an alkali metal complex ion.