Ammonium bis­(salicyl­aldehyde thio­semi­car­ba­zonato)ferrate(III), a supra­molecular material containing low-spin Fe(III)

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.