SYNTHESIS, STRUCTURE AND MAGNETISM OF IRON-(III) AND IRON-(II) COMPLEXES OF 1-THIA-4,7-DIAZACYCLONONANE AND N,N'-DIMETHYL-1-THIA-4,7-DIAZACYCLONONANE

The mononuclear complexes [Fe([9]aneN(2)S)Cl-3] and [Fe(Me(2)[9]aneN(2 )S)Cl-3] ([9]aneN(2)S = 1-thia-4,7-diazacyclononane, Me(2)[9]aneN(2)S = N,N'-dimethyl-1-thia-4,7-diazacyclononane) have been prepared by add ition of the cyclononane to an ethanolic solution of FeCl3. mu-Oxo-bis (mu-acetato)diiron(III) complexes [Fe2O(O(2)CMe)(2)([9]aneN(2)S)(2)[PF 6](2) and [Fe2O(O(2)CMe)(2)(Me(2)[9]aneN(2)S)(2)][PF6](2) have been sy nthesised by addition of sodium acetate tb suspensions of the mononucl ear complexes and isolated as the hexafluorophosphate salts. The iron( rr) dimer [Fe-2(OH)(O(2)CMe)(2)(Me(2)[9]aneN(2)S)(2)]ClO4 was prepared under anaerobic conditions. The four iron(III) complexes were charact erised by crystal structural studies. On the bases of the isomer shift and quadrupole splitting observed in the Mossbauer spectra of the dim ers (4.2 K) the iron-(III) and -(II) ions were determined to be in the high-spin configuration. The magnetic susceptibility (300-4.2 K) of [ Fe2O(O(2)CMe)(2)([9]aneN(2)S)(2)][PF6](2) (H = -2JS(1) . S-2) indicate d that the iron(In) sites were antiferromagnetically coupled (J = - 12 5 cm(-1)). In the case of the iron(rr) dimer J = -7.4 cm(-1). The diff erences observed in the redox behaviour of [Fe2O(O(2)CMe)(2)([9]aneN(2 )S)(2)][PF6](2) and FeO)-O-2(O(2)CMe)(2)(Me(2)[9]aneN(2)S)(2)][PF6](2) are attributed to the presence of the sterically demanding ligand met hyl substituents.