2-(1H-Tetrazol-1-yl)thiazole: Complexation and copper-assisted tetrazole ring transformation

Abstract 2-(1H-Tetrazol-1-yl)thiazole (tth), prepared by heterocyclization of 2-aminothiazole with triethyl orthoformate and sodium azide, was found to react with copper(II) chloride in ethanol giving a mixture of [Cu(tth)2Cl2]n (1) and [Cu2(ethc)2Cl4]·2H2O (2) , where ethc is ethyl thiazol-2-ylcarbamimidate. Formation of complex 2 with ethc ligand can be explained by tetrazole ring-opening reaction of tth followed by addition of ethanol to the intermediate N-(thiazol-2-yl)cyanamide (N-tca). This assumption was confirmed by isolation of complex 2 under interaction of N-tca with copper(II) chloride in ethanol. Transformation of the tetrazole ring was not observed under interaction of tth and copper(II) chloride in 1,2-dichloroethane/ethanol mixture, when 1 and [Cu2(tth)4Cl4] (3) were isolated. Ligand tth was found to react with copper(II) tetrafluoroborate and cobalt(II) chloride giving [Cu(tth)2(H2O)4](BF4)2 (4) and [Co(tth)2Cl2(H2O)2]·2tth (5) , correspondingly. Molecular crystals of tth and complexes 1–5 were characterized by X-ray single crystal analysis. In the complexes, tth acts as a monodentate ligand coordinated via the tetrazole ring N4 atom.