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 Cu(I) 'U-shape' molecular clip with, respectively, the cyano CN(-), tricyanomethanide C(CN)(3)(-), and azido N(3)(-) 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 Cu(I)···Cu(I) distances within the molecular clips. The formation of these discrete metallacycles is rationalized by analyzing the structural features of the Cu(I) 'U-shape' molecular clip.