Recent developments in the chemistry of hofmann-type and the analogous clathrates

Based on the structural features of Hofmann-type clathraces M(NH₃)₂M'(CN)₄ · 2G (M = a divalent metal in six-coordination, M' = a divalent metal in square-planar coordination, G = a small aromatic guest molecule), several series of the analogous clathrates have been derived by appropriate replacements of the host moieties. These clathrates are designated with a general formula Cd (diam)M'(CN)₄ ·$\text{n}$G where diam refers to diammine, an ambident diamine or monoethanolamine (mea), or a pair of unidencate mea's, M'(CN)₄ is a square-planar or a tetrahedral tetracyanometallate(II), and G is a small aromatic guest molecule. The number of guest molecules, $\text{n}$, varies stepwise from 2 through $\text{3}\text{2}$ to 1 depending on the bulkiness of diam ligand which builds up the host structure. Their structural features are discussed on the two- and three-dimensional networks of the metal complex hosts. The historical background is also reviewed briefly.