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

• Published in: Polyhedron 2019-10, Vol.171, p.423-432
• Main Authors: Voitekhovich, Sergei V., Grigoriev, Yuri V., Lyakhov, Alexander S., Matulis, Vadim E., Ivashkevich, Ludmila S., Ivashkevich, Oleg A.
• Format: Article
• Language: English
• Subjects: Copper(II); Cyanamides; Metallocomplexes; Tetrazoles; Thiazoles
• ISSN: 0277-5387
• DOI: 10.1016/j.poly.2019.07.030

Despite the arrangement of donor centers suggesting chelation, 2-(1H-tetrazol-1-yl)thiazole is coordinated by only N4 atom of the tetrazole cycle in copper(II) and cobalt(II) complexes. Under interaction with copper(II) chloride and ethanol it also undergoes tetrazole ring transformation leading to ethyl thiazol-2-ylcarbamimidate complex. [Display omitted] 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.