Bis{[amino-(iminium-yl)meth-yl]urea} tetra-kis-{2-[(di-methyl-amino)(iminium-yl)meth-yl]guanidine} di-μ-oxido-tetra-μ-oxido-tetra-deca-μ-oxido-octa-oxidodeca-vanadium(V) tetra-hydrate.

The title compound, (CHN)(CHNO)[VO]·4HO, is a by-product obtained by reacting ammonium metavanadate(V), metformin hydro-chloride and acetic acid in the presence of sodium hypochlorite, at pH = 5. The crystal structure comprises a deca-vanadate(V) anion (VO) lying on an inversion centre in space group , while cations and solvent water mol-ecules are placed in general positions, surrounding the anion, and forming numerous N-H⋯O and O-H⋯O hydrogen bonds. Metforminium (CHN) and guanylurea (CHNO) cations display the expected shape.