Employing Lewis Acidity to Generate Bimetallic Lanthanide Complexes.

With the advent of lanthanide-based technologies, there is a clear need to advance the fundamental understanding of 4f-element chelation chemistry. Herein, we contribute to a growing body of lanthanide chelation chemistry and report the synthesis of bimetallic 4f-element complexes within an imine/hemiacetalate framework, [Ln = lanthanide; TPT = tris(pyridineimine)(Tren)tris(methoxyhemiacetalate); Tren = tris(2-aminoethylamine)]. These products are generated from hydrolysis and methanolysis of the cage ligand tris(pyridinediimine)bis(Tren) (; Tadanobu et al. , (5), 859-862) likely facilitated by inductive effects stemming from the Lewis acidic lanthanide cations. These complexes are interesting because they result from imine cleavage to generate two metal binding sites: one pocketed site within the macrocycle and the other terminal site capping a hemiacetalate moiety. A clear demarcation in reactivity is observed between samarium and europium, where the lighter and larger lanthanides generate a mixture of products, and . Meanwhile, the heavier and smaller lanthanides generate exclusively bimetallic . The cleavage reactivity to form was extended beyond methanol to include other primary alcohols.