Synthesis, structure and magnetism of iron-( III ) and -( 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 addition of the cyclononane to an ethanolic solution of FeCl 3 . µ-Oxo-bis(µ-acetato)diiron(III) complexes [Fe 2 O(O 2 CMe) 2 ([9]aneN 2 S) 2 ][PF 6 ] 2 and [Fe 2 O(O 2 CMe) 2 (Me 2 [9]aneN 2 S) 2 ][PF 6 ] 2 have been synthesised by addition of sodium acetate to suspensions of the mononuclear complexes and isolated as the hexafluorophosphate salts. The iron(II) dimer [Fe 2 (OH)(O 2 CMe) 2 (Me 2 [9]aneN 2 S) 2 ]ClO 4 was prepared under anaerobic conditions. The four iron(III) complexes were characterised by crystal structural studies. On the bases of the isomer shift and quadrupole splitting observed in the Mossbauer spectra of the dimers (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 [Fe 2 O(O 2 CMe) 2 ([9]aneN 2 S) 2 ][PF 6 ] 2 (ℋ = -2JS 1 ·S 2 ) indicated that the iron(III) sites were antiferromagnetically coupled (J = -125 cm -1 ). In the case of the iron(II) dimer J = -7.4 cm -1 . The differences observed in the redox behaviour of [Fe 2 O(O 2 CMe) 2 ([9]aneN 2 S) 2 ][PF 6 ] 2 and [Fe 2 O(O 2 CMe) 2 (Me 2 [9]aneN 2 S) 2 ][PF 6 ] 2 are attributed to the presence of the sterically demanding ligand methyl substituents.

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