POTASSIUM TRANS-TETRAQUARDICARBONATONICKELATE(II), K2[NI(CO3)2(H2O)4]

The structure of potassium tetraaquadicarbonato-nickelate(II), K2[Ni(C O3)2(H2O)4], can be described as a close-packed arrangement of [Ni(CO3 )2(H2O)4]2-anions at the corners and the body centre of the monoclinic unit cell with K+ cations located in the interstices. Each Ni atom is coordinated by four water 0 atoms and two monodentate carbonate 0 ato ms arranged in a trans configuration at the corners of a slightly dist orted octahedron, with Ni-O bond distances in the range 2.046 (2)-2.09 4 (3) angstrom. Hydrogen bonding takes place between water molecules a nd carbonate groups within and between the anions. The anions are link ed into a three-dimensional network by the hydrogen bonding. Each K+ i on has seven neighbouring 0 atoms at normal distances ranging from 2.6 99 (3) to 3.094 (3) angstrom. The carbonate group exhibits a deviation from D3h symmetry [O-C 1.275 (4)1. 292 (5) angstrom; O-C-0 119.5 (3)- 120.5 (3)-degrees].