title: Hydrogen bonding in diaquatetrakis(urea-kappaO)M(II) dinitrates, with M = Ni and Co.
abstract: The isomorphous title compounds, [Ni{(NH(2))(2)CO}(4)(H(2)O)(2)](NO(3))(2) and [Co{(NH(2))(2)CO}(4)(H(2)O)(2)](NO(3))(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.
authors.affiliation: Faculty of Chemistry, Jagiellonian University, Ingardena 3, 30-060 Krakow, Poland. krawczuk@chemia.uj.edu.pl
authors.forename: Anna
authors.initials: A
authors.lastname: Krawczuk
authors.forename: Katarzyna
authors.initials: K
authors.lastname: Stadnicka