The chemistry of known metal thiocyanates is very rich and despite this richness, there are likely many more compounds to be discovered. The binary compounds presently known can be separated into five broad categories: the layered octahedral structures derived from the Ni(NCS) 2 structure type; the distorted fluorite eight-coordinate structures analogous to Ba(NCS) 2 ; the polymorphic tetrahedral structures found for Cu(I) and Ag(I); the ionic NaCl and CsCl derived structures found for group 1 and Tl + thiocyanates; and the complex framework structures found for the d 10 and p-block metals. These categories will likely become clearer as more structures are discovered, and there are 37 metal thiocyanates yet to be structurally characterized, of which 24 have not yet been reported at all. Ternary thiocyanates naturally adopt a wider range of structures than the binaries. Two general themes are the prevalence of perovskitoid and diamondoid structures and the frequency with which a mixture of soft and hard metals occurs. There are undoubtedly many more ternary structures feasible, let alone quaternary or higher order compositions. The complexity of some of these structures is such that crystallography has been essential to determine the basic chemistries, with simple IR spectroscopic rules of thumb sometimes being misleading.