Abstract
The synthesis and crystal structure (100 K) of the title compound, ammonium bis[salicylaldehyde thiosemicarbazonato(2-)-κ(3)O,N(1),S]iron(III), NH(4)[Fe(C(8)H(7)N(3)OS)(2)], is reported. The asymmetric unit consists of an octahedral [Fe(III)(thsa)(2)](-) fragment, where thsa(2-) is salicylaldehyde thiosemicarbazonate(2-), and an NH(4)(+) cation. Each thsa(2-) ligand binds via the thiolate S, the imine N and the phenolate O donor atoms, resulting in an Fe(III)S(2)N(2)O(2) chromophore. The ligands are orientated in two perpendicular planes, with the O and S atoms in cis and the N atoms in trans positions. The Fe(III) ion is in the low-spin state at 100 K. The crystal structure belongs to a category I order-disorder (OD) family. It is a polytype of a maximum degree of order (MDO). Fragments of the second MDO polytype lead to systematic twinning by pseudomerohedry.