Synthesis of Small Tetranuclear Cu(I) Metallacycles Based on Bridging Pseudohalogenide Ions

Three new ‘short’ metallacycles are selectively obtained from the reaction of a bimetallic CuI ‘U-shape’ molecular clip with, respectively, the cyano CN–, tricyanomethanide C­(CN)3–, and azido N3– pseudohalogenide ions. These supramolecular assemblies have been characterized by spectroscopic methods, single-crystal X-ray diffraction, and elemental analysis. The single-crystal X-ray structures of these complexes reveal no short contact interaction between the pseudohalogenide ions within these self-assembled structures despite the short CuI···CuI distances within the molecular clips. The formation of these discrete metallacycles is rationalized by analyzing the structural features of the CuI ‘U-shape’ molecular clip.