How Robust Is the N−H···Cl2−Cu Synthon? Crystal Structures of Some Perchlorocuprates

A series of perchlorocuprate salts, namely, [4,4‘-H 2 diazastilbene][CuCl 4 ] 1, [H 2 - N -(4-pyridyl)isonicotinamide][CuCl 4 ] 2, [H 2 - N -(3-pyridyl)isonicotinamide][CuCl 4 ] 3, [H 2 - N -(4-pyridyl)nicotinamide][CuCl 4 ] 4, [H 2 - N, N ‘-bis(4-pyridyl)urea][CuCl 4 ] 5, [H-isonicotinic acid] 2 [CuCl 4 ]2H 2 O 6, [2-aminopyridinium] 2 [CuCl 4 ] 7, and [3-aminopyridinium] 2 [CuCl 4 ] 8 have been synthesized and analyzed by single-crystal X-ray diffraction. The results indicate that N−H···Cl−Cu hydrogen-bonding interaction is important in supramolecular syntheses of these solids. However, occurrence of bifurcated hydrogen bonding of the type N−H···Cl 2 Cu (synthon A) appears to be dependent on the topology of the cations, geometry of the anions, and other weak interactions such as C−H···Cl−Cu. Salts of isomeric cations such as 2, 3 and 4, and 7 and 8 are crystallographically isostructural in their respective groups despite having different hydrogen-bonding site topologies. The hydrogen-bonding-capable backbones (amide and urea moieties) in 2, 3, 4, and 5 do not display the typical hydrogen-bonding network involving these moieties.