Heterotrimetallic sandwich complexes supported by sulfonamido ligands

Co^II complexes bearing sulfonamido ligands derived from tris(2-aminoethyl)amine (H₆tren) assemble into complex architectures in the presence of Group II ions through interactions between the Group II ion and the sulfonyl oxygens. Novel ligands where the sulfonyl groups bear tert-butyl substituents afford well-defined isostructural heterotrimetallic sandwich complexes where two anionic [LCo^II]⁻ fragments are bridged by a Group II metal ion (Mg²⁺, Ca²⁺, Sr²⁺, or Ba²⁺). Solution studies on these novel sandwich complexes by cyclic voltammetry and electronic absorption spectroscopy indicate that these structures are not dramatically altered in solution, opening the door to the exploration of reactivity at Co^II that is modified by Group II ions.