and conformers of di-ammonium aqua-bis(malonato)oxidovanadate(IV) in an anhydrate crystal.

The asymmetric unit of the title anhydrate compound, (NH)[VO(CHO)(HO)], consists of two independent complex anions and four ammonium cations. In the complex anions, the V atoms are each coordinated by two malonate ligands, one water mol-ecule and one oxide O atom in a distorted octa-hedral geometry. The equatorial plane is formed by the malonate O atoms, while the axial positions are occupied by water and oxide O atoms. The difference between the two independent complexes is the relative conformation of the malonate ligands. The two ligands in one complex anion are in a conformation, while in the other they adopt an conformation. In the crystal, the complex anions inter-act with the counter-cations and adjacent anions through O-H⋯O, N-H⋯O and C-H⋯O hydrogen bonds. Stacks of alternating layers consisting of either or isomers, formed with the aid of the hydrogen bonding, are observed. DFT calculations for the and isomers show a similar thermodynamic stability to each other. The crystal used for this analysis was an inversion twin with the ratio of the twin components being 0.270 (13):0.730 (13).