Crystal structure of Ba₂Co(BO₃)₂

Abstract

Single crystals of dibarium cobalt(II) bis(orthoborate), Ba 2 Co(BO 3 ) 2 , have been obtained from the melt. The crystal structure is composed of two isolated (BO 3 ) 3− triangles linked to Co 2+ cations. The resulting [CoO 5 ] square pyramids and the borate anions make up branched rows extending parallel to [010]. The barium cations occupy two sites in the voids of this arrangement and exhibit coordination numbers of nine each. A comparison with the structures of other A 2 M (BO 3 ) 2 compounds reveals a unique five-coordination of the small metal M in the title compound instead of four- or six-coordination for the other A 2 M (BO 3 ) 2 compounds with M = Cu, Zn, Mg, Ca, or Cd.