Crystal structure of K 6 [Zn(CO 3 ) 4 ].

The crystal structure of K 6 [Zn(CO 3 ) 4 ], hexa-potassium tetra-carbonato-zincate(II), comprises four unique potassium cations (two located on a general position, and two on the twofold rotation axis of the space group C 2/ c ) and a [Zn(CO 3 ) 4 ] 6- anion. The Zn II atom of the latter is located on the twofold rotation axis and is surrounded in a slightly distorted tetra-hedral manner by two pairs of monodentately binding carbonate groups, with Zn-O distances of 1.9554 (18) and 1.9839 (18) Å. Both carbonate groups exhibit a slight deviation from planarity, with the C atom being shifted by 0.008 (2) and 0.006 (3) Å, respectively, from the plane of the three O atoms. The coordination numbers of the potassium cations range from 6 to 8, using a threshold of 3.0 Å for K-O bonding inter-actions being significant. In the crystal structure, [KO x ] polyhedra and [Zn(CO 3 ) 4 ] 6- groups share O atoms to build up the framework structure.