Cd 2 [M 11 (CN) 6 ]·8H 2 O, where M=Fe, Ru and Os, form a family of isomorphous compounds which crystallize in the monoclinic P2 1 /n space group. M 11 cations present their usual octahedral coordination, while the cadmium atom coordinates to three nitrogen atoms from the cyanide groups and three water molecules forming a distorted octahedron. The rest of the water molecules are located in small channels in the structure and are hydrogen bonded to the coordinated ones. Adjacent cadmium octahedra share one edge to form the moiety: Cd 2 N 6 (H 2 O) 4 , in such a way that two metal sequences are observed: M 11 -Cd-M 11 , forming a tridimensional network. Coordinated and zeolitic water molecules can be removed preserving the M-C=N-Cd framework. © 2001 Published by Elsevier Science Ltd.