The binuclear cation of the title compound, [Ni(2)(C(33)H(29)N(4)O(3))(H(2)O)(4)]C(2)H(3)O(2).C(3)H(7)NO.0. 75H(2)O, was synthesized as a model for the active site of urease. Two tridentate halves of the symmetrical 2, 6-bis[(2-hydroxyphenyl)(2-pyridylmethyl)amino]methyl-4-methylphenol ate (BPPMP(3-)) ligand are arranged in a meridional fashion around the two Ni(II) ions, with the phenoxo O atom bridging the Ni(II) ions. The cation has an approximate twofold rotation axis running through the C-O bond of the bridging phenolate group. Four water molecules complete the octahedral environment of each Ni(II) ion.