Hydrogen bonding in diaquatetrakis(urea‐κO)MII dinitrates,with M = Ni and Co

The isomorphous title compounds, Ni{(NH₂)₂CO}₄(H₂O)₂](NO₃)₂ and Co{(NH₂)₂CO}₄(H₂O)₂](NO₃)₂, feature discrete centrosymmetric cations in octahedral coordinations, formed by four urea molecules linked via their O atoms to the central ion in equatorial positions and two water molecules in trans positions. The complexes are packed in a pseudo‐hexagonal manner separated by the nitrate counter‐ions. All H atoms are involved in moderate hydrogen bonds of four types: N—H...O=C, N—H...O—N, O—H...O—N and N—H...O—H. Graph‐set analysis was applied to distinguish the hydrogen‐bond patterns at unitary and higher level graph sets.