Neutral diiron(III) complexes with Fe2(mu-E)2 (E = O, S, Se) core structures: reactivity of an iron(I) dimer towards chalcogens

Three neutral bis(?-chalcogenido)diiron(iii) complexes, [ (N,N -Pipiso)Fe(?-E) 2] (Pipiso- = [(DipN)2C(cis-2,6-Me2NC5H8)]-, (Dip = C6H3Pri 2-2,6; E = O, S or Se) have been prepared by reactions of the iron(i) dimer [ (?-N,N -Pipiso)Fe 2] with O2, S8 or Se8. Treating the ?-selenido compound [ (N,N -Pipiso)Fe(?-Se) 2] with O2 cleanly generated its ?-oxo counterpart, [ (N,N -Pipiso)Fe(?-O) 2]. X-ray crystallographic analyses of the compounds showed them to possess Fe2(?-E)2 core structures with distorted square planar (E = O) or tetrahedral (E = S or Se) iron coordination geometries. Magnetic, 57Fe Mossbauer spectroscopic and computational studies indicate medium to strong antiferromagnetic coupling between the two high-spin FeIII ions in all three compounds.