[[Ba2(C2O4)(H2O)6](NCS)2]n: a layered mixed-anion barium oxalate.

We present the first example of a compound containing Ba2+, C2O42-, water and some additional halide or pseudo-halide anions, viz. hexa-mu2-aqua-mu6-oxalato-dibarium(II) diisothiocyanate, [[Ba2(C2O4)(H2O)6](NCS)2]n. The structure consists of positively charged planar covalent layers of Ba2+ cations, oxalate anions and water molecules. The first coordination sphere of the Ba2+ cation contains six water molecules and four O atoms from two planar oxalate anions. The oxalate anion lies on an inversion centre and is coordinated to six Ba2+ cations, each donor O atom being bonded to two cations. Pairs of water molecules are coordinated by two Ba2+ cations. The layers are interspersed with non-coordinated NCS- anions.