Bis[4-amino-N-(pyrimidin-2-yl)benzenesulfonamido]diamminecopper(II): aqua or ammine ligands?

Diffraction results obtained at 100 and 291 K, the former at high resolution, are reported for the title compound, [Cu(C10H9N4O2S)2(NH3)2] or [Cu(sulfa)2(NH3)2] [Hsulfa is 4‐amino‐N‐(pyrimidin‐2‐yl)benzenesulfonamide]. The CuII cation is coordinated by two N‐atom donors from a bidentate sulfa ligand, by two ammonia molecules in the equatorial plane and by a monohapto (η1) sulfadiazine at the apex of a distorted square pyramid. The present interpretation and two earlier reports [Brown, Cook & Sengier (1987). Acta Cryst. C43, 2332–2334; Tommasino, Renaud, Luneau & Pilet (2011). Polyhedron, 30, 1663–1670] disagree about the nature and geometry of the ligands. The relationship between the present result and the former is discussed, and evidence is provided that the latter erroneously assigned an ammine as an aqua ligand.