Iron complexes of N-substituted thiosalicylideneimines. Part 3. Structure, magnetism, and Mössbauer spectra of the complex chloro[N,N′-ethylenebis(thiosalicylideneiminato)]iron( III ), an intermediate-spin complex which exists in three crystalline forms

Chloro[N,N′-ethylenebis(thiosalicylideneiminato)]iron(III), [Fe(tsalen)Cl], has been prepared by reaction of [Tl2(tsalen)] with anhydrous FeCl3. A crystal-structure determination has revealed the existence of three modifications of the complex. The α form predominates (96%) and contains equal numbers of weakly interacting Fe–S bridged dimer units (type 1 molecules) and monomers (type 2 molecules) with the Fe having a square-based pyramidal distribution of bonds. The β form consists of monomer species alone, while the γ form has weakly interacting dimer units. A variable-temperature magnetic study and Mössbauer spectral measurements on a bulk sample of the complex indicate that the Fe atoms have the intermediate S= spin state.