There are currently 23 binary metal thiocyanates with reported crystal structures (Fig. ). They can be divided into five categories: van der Waals layered structures with octahedral metals analogous to the NiI 2 structure-type in halide (Section 2.1); 3D framework structures with eight-coordinate metals with highly distorted CaF 2 -derived structures (Section 2.2); tetrahedral frameworks found for coinage metal monovalent cations related to CuI (Section 2.3); ionic structures analogous to NaCl and CsCl found for alkali metals and Tl + (Section 2.4) and a variety of complex, 1D, 2D and 3D frameworks adopted by groups 12, 14, and 15 metals (Section 2.5).