Substitutional/positional disorder of biguanide and guanylurea in the structure of a decavanadate complex [(Bg)(HVO)][(HGU)(VO)](HMet)(HO)·8HO.

A hydrated salt of decavanadate containing diprotonated metforminium(2+) (HMet), hydronium (HO) and either neutral biguanide (Bg) or monoprotonated guanylurea (HGU) exhibits a previously seen complex charge-stabilized hydrogen-bonded network [Chatkon et al. (2022). Acta Cryst. B78, 798-808]. Charge balance is achieved in two ways through substitutional disorder: a 0.6 occupied HGU cation is paired with a VO anion, and a 0.4 occupied neutral Bg molecule is paired with a HVO anion, with the remaining charge in both cases balanced by two HMet dications and one HO monocation. Bg/HGU moieties exhibit bifurcated N-H...O hydrogen bonding to the HO cation and are substitutionally/positionally disordered along with the HO cation about an inversion center. The HGU VO synthon seen in the previous study occurs again. Bg exhibits bifurcated hydrogen bonding from two amino groups to two rows of cluster O atoms running diagonally across the equatorial plane of the HVO anion with a return hydrogen bond from the cluster H atom to the imino N atom of the Bg. Thus, a Bg...cluster synthon similar to the HGU...cluster synthon previously reported is found. The disordered moieties occupy spaces with excess volume in the 3-D network structure. Interestingly, when the crystallographic unit cell of the current compound, whose X-ray data was collected at 100 K, is compared with that of a previous compound exhibiting the same supramolecular framework, unit-cell parameter c does not shorten as a and b expectantly do because of the lower data collection temperature. The lack of contraction on unit-cell parameter c is possibly due to the supramolecular structure.