and S-termini: the N-terminus is harder and typically coordinates well to harder first row transition metals and s-block metals; the S-terminus is softer, and most often coordinates to soft metals (late transition metals, 4d-, 5d-transition metals and late p-block metals). This asymmetry means that binary thiocyanates are harder to form that might otherwise be expected, because often thiocyanate will readily coordinate through one terminus (Nor S-) to a given metal but only bind weakly through the other end, meaning other ligands (including solvents such as water) can bind more strongly than thiocyanate itself. A common challenge in the synthesis of binary thiocyanates is therefore removing or avoiding competing ligands and coordinating solvents. The large chemical differences between N and S do offer opportunities for ternary phases however, and this has been exploited in the synthesis of cation-ordered ternary frameworks (see Section 3). The difference in bonding between termini can also be seen in the metal and thiocyanate bond angle: the experimental M-NCS angle distribution peaks at 180º and the M-SCN angle distribution centres on around 100º , due to the shapes of the frontier orbitals. The bent M-SCN angle, together with the rod-like shape of thiocyanate means that the symmetries of metal thiocyanates are typically lower than of equivalent halides. This desymmetrization means that the structures are well-ordered, aside from highly ionic salts, in contrast to unlike CN -where the pseudosymmetry produces extensive disorder. The head-tail order also offers new routes for polymorphism (e.g. Section 2.3). A wide variety of coordination modes are adopted by NCS -: total coordination numbers vary from two to eight, with S and N coordination numbers going from zero to four (Fig. ). In general, the sulfur terminus tends to adopt higher coordination numbers than the nitrogen terminus in the same compound. The differences in local bonding discussed also have consequences for their electronic structures and semiconducting properties.