The stability of Ni2+, Cu2+, and Zn2+ complexes with a bis(tetradentate) compartmental pyrazolate ligand (L) was determined in aqueous solution at 25 degreesC and I=0.5 M (KNO3). Thereby a series of mononuclear [MLHn] (n=2, 1, 0, -1, and -2) and dinuclear species [M2LHm] (m= 0, -1, -2) was observed. The stability of [ML] and [M2L] increases in the order Ni2+< Zn2+< Cu2+, whereby in the case of Ni2+ no dinuclear species could be detected. Structural proposals for several species were corroborated by X-ray diffraction studies. In all cases the pyrazolate group has a pronounced tendency to bridge two metal ions.