N,N′-Dimethylene-2,2′-biimidazole—A Mimic of Carboxylate for the Formation of Complexes with Copper(I) And the Anion Directed Formation of a Solvent Pocket

Abstract

The reaction of N,N′-dimethylene-2,2′-biimidazole (L) with various copper salts gives eight complexes that were characterized structurally in the solid state. This showed that the ligand can effectively bridge two copper atoms in close proximity similarly to the well-known bridging carboxylate motif. In reaction with copper(II), this gives a dimer (acetate, 1) or quadruple helicate (perchlorate, 2). Extention to copper(I) with a coordinating counterion gives a one-dimensional polymer (iodide, 3), while reaction with noncoordinating counterion gives M2L3 triple helicate motifs. These helicates were found to form chiral solvate-containing pockets surrounding benzene when combined with a three-fold symmetric anion (BF4–, ClO4– and NO3–, 4, 5, and 6, respectively) or an achiral complex with only acetonitrile (ClO4–, 7). While the pocket could accommodate fluorobenzene (BF4–, 8), more highly substituted benzenes do not allow its formation.