The remaining binary metal thiocyanates, Sn(NCS) 2 , Bi(NCS) 3 , Sb(NCS) 3 , 95 Cd(NCS) 2 and Zn(NCS) 2 98 each adopt a unique structures (Fig. ). Zn(NCS) 2 has a tetrahedrally coordinated Zn, with two distinct sites, one ZnN 4 and the other ZnS 4 , and four distinct NCS -anions each of which bridges two Zn atoms. This leads to a P1 van der Waals layered structure, analogous to the SiO 2 bilayer. The first report of the structure of Zn(NCS) 2 refers to it as β -Zn(NCS) 2 , which implies the existence of α-Zn(NCS) 2 , perhaps of lower symmetry, and although the analogy to SiO 2 suggests polymorphism is feasible, I have found no further details of an alternate phase.