Displacement of a cyclopentadienyl ligand by a crown ether from a Ianthanocene(II) [LnCp"2];: crystal structures of the first cationic lanthanoid(II) complexes, [SmCp"([18]-crown-6)][SmCp"3]•0.5C6H6 and [YbCp"([18]-crown-6)][Cp"]•3C6H6 [Cp" = η5-C5H3(SiMe3)2-1,3]

Treatment of [SmCp "(2)] or [YbCp "(2)] with [18]-crown-6 in benzene at ambient temperature yields the X-ray characterised, crystalline salts [SmCp "([18]-crown-6)][SmCp "(3)] 0.5C(6)H(6)1 and [YbCp "([18]-crown-6)] [Cp "] . 3C(6)H(6) 2; 1 with K in toluene affords [K([18]-crown-6)(eta(2)-PhMe)(2)]-[SmCp "(3)], also accessible from [SmCp "(2)], K[Cp "] and [18]-crown-6 in toluene [Cp " = eta(5)-C5H3(SiMe3)(2)-1,3].