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

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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.

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... It yielded, apart from three metal complexes, a polycyclic piperidine compound 10, which was a product of a complicated electron transfer between amine and Cu 2+ . It is to be noted that copper(II)-assisted transformations of organic substrates often accompany the coordination chemistry of this metal ion [28][29][30][31][32][33][34][35]. Our study provides the basis for the ongoing work on the reduction of copper(II) with piperidine and its homologs. ...
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Published data on the synthesis, structure, properties and applications of metal derivatives of tetrazoles are generalised and described systematically. Compounds based on the anionic and neutral tetrazole forms, C- and N-mono- and C,N-disubstituted tetrazoles are considered.
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The dinuclear nickel(II) complex [Ni2L(μ-ClO4)]ClO4, where L2– represents a 24-membered macrocyclic bis(triamine–thiophenolate) ligand, reacts with 1-methyltetrazole-5-thiol and triethylamine to give the complex [Ni2L(μ-SCN4Me)]ClO4, which was subjected to metathesis with NaBPh4 yielding [Ni2L(μ-SCN4Me)]BPh4. This new complex was characterized by elemental analysis, UV/Vis/NIR and IR spectroscopy. The structure of [Ni2L(μ-SCN4Me)]BPh4 was determined by X-ray crystallography, showing the 1-methyltetrazole-5-thiolate ligand in an N(3),N(4)-bridging mode generating a bis(octahedral) N3Ni(μ-S)2(μ-SCN4Me)NiN3 core. Quantum chemical calculations of the molecular electrostatic potential, natural population analysis and total energies of possible structures of [Ni2L(μ-SCN4Me)]+ are in agreement with the structural data obtained. Temperature-dependent magnetic susceptibility measurements revealed that the NiII ions in the dinuclear complex are weakly ferromagnetically coupled showing a coupling constant J of 19.5 cm–1 (H = –2JS1S2).
Article
The unambiguous discrimination between 1-substituted and 2-substituted tetrazoles as well as between 1,5- and 2,5-disubstituted tetrazoles by means of homonuclear NOE difference spectroscopy is described.Die Unterscheidung zwischen 1-substituierten und 2-substituierten bzw. zwischen 1,5- und 2,5-disubstituierten Tetrazolen mittels NOE Differenzspektroskopie wird beschrieben.
Article
Despite the remarkable thermochemical accuracy of Kohn–Sham density-functional theories with gradient corrections for exchange-correlation [see, for example, A. D. Becke, J. Chem. Phys. 96, 2155 (1992)], we believe that further improvements are unlikely unless exact-exchange information is considered. Arguments to support this view are presented, and a semiempirical exchange-correlation functional containing local-spin-density, gradient, and exact-exchange terms is tested on 56 atomization energies, 42 ionization potentials, 8 proton affinities, and 10 total atomic energies of first- and second-row systems. This functional performs significantly better than previous functionals with gradient corrections only, and fits experimental atomization energies with an impressively small average absolute deviation of 2.4 kcal/mol.