Organic–inorganic hybrid mixed-halide Zn(II) and Cd(II) tetra­halometallates with the 2-methyl­imidazo[1,5-a]pyridinium cation

Three isomorphous 0-D hybrid salts, namely, 2-methyl­imidazo[1,5-a]pyridinium tri­chlorido­iodido­zincate(II), (C(8)H(9)N(2))(2)[ZnCl(3.19)I(0.81)] or [L](2)[ZnCl(3.19)I(0.81)], (I), 2-methyl­imidazo[1,5-a]pyridinium di­bromido­dichlorido­cadmate(II), (C(8)H(9)N(2))(2)[CdBr(2.42)Cl(1.58)] or [L](2)[CdBr(2.42)Cl(1.58)], (II), and 2-methyl­imidazo[1,5-a]pyridinium tri­chlorido­iodido­cadmate(II), (C(8)H(9)N(2))(2)[CdCl(3.90)I(0.10)] or [L](2)[CdCl(3.90)I(0.10)], (III), are assembled from discrete 2-methyl­imidazo[1,5-a]pyridinium cations, L (+), and mixed-halide tetra­halometallate anions. In the three structures, there are two crystallographically non-equivalent cations that were modelled as being rotationally disordered by 180°. In the lattices of the three compounds, a disordered state exists involving partial substitution of Cl by I for sites 2–4 in (I), Br by Cl for all four sites in (II) and Cl by I for site 2 in (III). In the solid state, the organic and inorganic sheets alternate parallel to the bc plane in a pseudo-layered arrangement. In the organic layer, pairs of centrosymmetic­ally related trans-oriented cations form π-bonded chains. The adjacent tetra­halometallate anions in the inorganic layer show no connectivity with the shortest M⋯M separations being greater than 7 Å. A variety of C—H⋯X—M (X = Cl, Br, I) contacts between the organic and inorganic counterparts provide additional structural stabilization. The title structures are isomorphous with the previously reported structures of the chloride analogues, [L](2)[ZnCl(4)] and [L](2)[CdCl(4)].