The reaction of nickel(II) nitrate hexahydrate with the protontransfer compound (pnH2)2(btc)2H2O (where pn = propane- 1,3-diamine and btcH4 = benzene-1,2,4,5-tetracarboxylic acid) in aqueous solution resulted in the formation of the title compound, {(C3H12N2)[Ni(C10H2O8)(H2O)2]0.5H2O}n. Each Ni2+ ion is situated on a crystallographic twofold rotation axis and is coordinated in a distorted octahedral geometry by six O atoms [Ni—O = 2.0540 (15)–2.0804 (11) A ˚ ] from two water molecules and four btc4 ligands, which also act as bridging ligands between Ni2+ ions. In the crystal structure, intermolecular O—H O, N—H O and C—H O hydrogen bonds and C—H interactions contribute to the formation of a three-dimensional supramolecular structure. The crystal studied was an inversion twin.
