Organic–inorganic hybrid mixed-halide ZnII and CdII 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), (C8H9N2)2[ZnCl3.19I0.81] or [L]2[ZnCl3.19I0.81], (I), 2-methylimidazo[1,5-a]pyridinium dibromidodichloridocadmate(II), (C8H9N2)2[CdBr2.42Cl1.58] or [L]2[CdBr2.42Cl1.58], (II), and 2-methylimidazo[1,5-a]pyridinium trichloridoiodidocadmate(II), (C8H9N2)2[CdCl3.90I0.10] or [L]2[CdCl3.90I0.10], (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[ZnCl4] and [L]2[CdCl4].