Tetraaquabis(pyridine)metal(II) saccharinate tetrahydrate, [M(H2O)4(py)2](sac)2•4H2O; M = Co, Ni.: Crystal structure determination

The crystal structure determination of the title compounds showed that they are isomorphous, revealing the general formula [M(H2O)(4)(py)(2)](sac)(2).4H(2)O. Their structures are built up of [M(H2O)(4)(py)(2)](2+) cations, saccharinato anions and non-coordinated water molecules. The metal atom lies on the inversion center and is octahedrally coordinated by four water oxygens and two pyridine nitrogen atoms. The crystal structure packing is achieved through the hydrogen bonds of O-w...O-w, O-w...O and O-w...N type. Coordinated water molecules are hydrogen bonded to non-coordinated ones at the same time participating in hydrogen bonding with carbonyl oxygen and nitrogen atom from the saccharinato anions. Non-coordinated water molecules participate in hydrogen bonding with the oxygen atoms belonging to the saccharinato CO and SO2 groups. The hydrogen bond network between the oxygen atoms belonging to the SO2 group of the saccharinato anions and one of the non-coordinated water molecules (OW3) constructs the centrosymmetric cavity in the structure.