Substituent-dependent coordination modes of 1-methyl-5-R-tetrazoles in their cupric chloride complexes

Abstract

A series of cupric chloride complexes with 1-methyl-5-R-tetrazole ligands, where R = NH2, t-Bu, Ph, MeS, CHCH2, MeSO2, were synthesized by interaction of CuCl2·2H2O with the above ligands LNH2, LtBu, LPh, LMeS, LVin, and LMeSO2, respectively. The obtained complexes [Cu(LNH2)3Cl2]·H2O (1), [Cu(LtBu)2Cl2] (2), [Cu(LPh)2Cl2] (3), [Cu(LMeS)2Cl2] (4), [Cu(LVin)Cl2]n (5), and [Cu(LMeSO2)(H2O)Cl2]n (6) were characterized by single crystal X-ray analysis. The effect of C5-substituent on coordination modes of tetrazole ligands and structural motifs of complexes was observed. Complexes 1–4 are mononuclear, with the tetrazole ring N4 coordination. Complex 5 presents 1D coordination polymer, formed at the expense of triple bridge between two neighboring copper(II) cations (double chlorido bridge and the tetrazole ring N3,N4-bridge). In 6, being also 1D coordination polymer, coordination chains are composed of alternating Cu(LMeSO2)2 and Cu(H2O)2 fragments linked by double chlorido bridges. Ligand LMeSO2 shows N3 coordination, being rare among 1,5-disubstituted tetrazoles. The influence of the nature of C5 substituents on coordination features of the obtained complexes is discussed by using quantum-chemical calculations of the electronic structure and basicity of the ligands.