Hydrogen-bonded Networks in Crown Ether Complexes of Hydrated Metal Ions

The hydrated metal nitrates (M(NO3)3.6H2O, M[dbnd]Co, Ni, Cu, Zn and Cd) have been crystallised from water in the presence of 18-crown-6 and their structures determined by X-ray crystallography. In the case of copper, a pseudo four-coordinate square planar complex resides in an extended six-coordinate octahedral array which is further bound in a single-stranded one-dimensional hydrogen bonded polymeric mode. For M[dbnd]Co,Ni,Zn and Cd isomorphous complexes are isolated where the octahedral [M(H2O)5(NO3)+ cation resides in a two-dimensional polymeric network through hydrogen bonds between the water ligands and either the crown ether oxygens or unbound nitrate ions or water molecules.