A pentadentate Schiff-base ligand 3,5Cl-L2- and NCSe- form an iron(iii) mononuclear complex, namely [Fe(3,5Cl-L)(NCSe)], which shows a thermally induced spin crossover with a broad hysteresis width of 24 K between 123 K (warming) and 99 K (cooling). Analogous complexes of the [Fe(3,5X-L)(Y)] type, where X = Cl or Br and Y = Cl-, N3-, NCS-, and NCSe-, are high-spin over the whole temperature interval.