Cyanometallates are good halogen bond acceptors for C− I and C− Br halogen bond donors and frequently crystallize in anhydrous form in the presence of halogen bonds, in contrast to most cyanometallate salts. Halogen bonds can involve interaction of the cyanide ligands via their exo lone pair or the CN π-bond. Halogen bond strength is related to metal-cyanide back bonding.
