Four Different Crystalline Products from One Reaction: Unexpected Diversity of Products of the CuCl2 Reaction with N-(2-Pyridyl)thiourea.

The reaction of N-(2-pyridyl)thiourea with CuCl2 in methanol yields four different crystalline products: yellow dimeric complex, [Cu2Cl2(?-Cl)2(L)2] (1), red polymeric complex, [Cu3Cl8L2]n (2), orange crystalline product with ionic structure, L2[CuCl4] (3), and colourless ionic compound LCl (4), where L = 2-amino-[1,2,4]thiadiazolo[2,3-a]pyridin-4-ium cation as a result of oxidative cyclization of N-(2-pyridyl)thiourea. The crystal structures of all these crystalline products have been determined by single-crystal X-ray diffraction analysis. Compound 1 involves a copper(I) ion while in 2 and 3 the copper centre is in the divalent state. 1H NMR spectra for compounds 1-3 are identical and confirm deprotonated thioamide groups of N-(2-pyridyl)thiourea and the formation of a thiadiazolopyridinium cation in solution. The hydrogen bonding and ?-? stacking interactions were investigated in the solid state. In addition, all crystalline products 1-4 exhibit also S···Cl bonding interactions which consolidate the complexes into networks. The X-ray diffraction analyses indicate the absence of other crystalline phases in the crude reaction mixture.