Hydrothermal reactions of 1-aminoethylidenediphosphonic acid (AEDPH4), Ni(OH)2 and ammonium counterions afforded two nickel phosphonate compounds, (enH2)3[Ni(AEDP)2] · 6H2O (1) and (NH4)6[Ni(AEDP)2] · 4H2O (2) (en = ethylenediamine). Compounds 1 and 2 both contain [Ni(AEDP)2]6- while having different three-dimensional (3-D) supramolecular structures. In 1, the [Ni(AEDP)2]6- anion and [image omitted]cations interconnected via various hydrogen bonds and form a 3-D porous supramolecular network with extended one-dimensional channels, in which an interesting T4(2)6(2) water tape penetrates. Compared to 1, the [Ni(AEDP)2]6- anion and [image omitted] cations in 2 constitute an enclosed 3-D supramolecular framework without obvious channels; two water-ammonium clusters with different structural motifs are observed. The magnetism of 1 exhibits weak antiferromagnetic interaction via the hydrogen bonds. The effect of protonated ammonium counterions on the structural types of the final products is also discussed. [ABSTRACT FROM AUTHOR]