Controlled synthesis of lanthanide–lithium inverse crown ether complexes

An ytterbium–lithium inverse crown ether complex stabilized by amine-bridged bis(phenolate) ligands (LYbBr)2(μ4-O)(μ3-Li) (1) [L = Me2NCH2CH2N{CH2-(2-O- C6H2-But2-3,5)}2] was isolated as a byproduct from the reaction of LYbCl(THF) with CH3Li in THF in a very low isolated yield. Further study revealed that the inverse crown ether complexes can be synthesized in a controlled manner by the reaction of bis(phenolate) lanthanide chloride with an in situ mixture of n-BuLi with water in THF. A second inverse crown ether complex (L′YbCl)2(μ4-O)(μ3-Li) (2) [L′ = Me2NCH2CH2N{CH2-(2-O-C6H2-But-3-Me-5)}2] was prepared in high isolated yield and well characterized.