While bis(1-methyl-1 H-tetrazol-5-yl)diazene, C4H6N10, (I), has no crystallographically imposed symmetry, in the two title chlorocopper(I) complexes, [Cu2Cl2(C4H6N10)] n, (II), and [CuCl(C4H6N10)] n, (III), the organic ligands lie across centres of inversion; in (III), the Cu and Cl atoms additionally lie about a twofold rotation axis in the space group P2/ c. Complex (II) forms a two-dimensional coordination polymer containing tetrahedrally coordinated CuI atoms, and complex (III) forms a one-dimensional coordination polymer containing five-coordinate square-pyramidal CuI atoms. [ABSTRACT FROM AUTHOR]