The molecular and electronic structure of the asymmetric, trinuclear complex [LFe III(μ-O) (μ-piv) 2Fe III(μ-OH)(μ-piv) 2Fe III(piv) 2]·C 6H 5CH 3 (L=1,4,7-trimethyl-1,4,7-triazacyclononane, piv=pivalate(1-))

Abstract

The synthesis and molecular structure as determined by single-crystal X-ray crystallography of the neutral complex [LFe III(μ-O)(μ-piv) 2Fe III(μ-OH)(μ-piv) 2Fe III(piv) 2]·C 6H 5CH 3 ( 1) are described (L=1,4,7-trimethyl-1,4,7-triazacyclononane; piv=pivalate(1-)). The electronic structure of 1 has been established by temperature-dependent susceptibility measurements (2–295 K), UV–Vis, EPR, and Mössbauer spectroscopy. The molecule possesses an S t=5/2 ground state. The two high-spin ferric ions bridged by an oxo group are strongly antiferromagnetically coupled ( H=−2 JS 1 S 2; S 1= S 2=5/2; J 12=−100 cm −1) whereas those bridged by a hydroxo group are less strongly antiferromagnetically coupled ( J 23=−14 cm −1). Complex 1 has been fully characterized by variable-temperature zero- and applied-field Mössbauer spectroscopy.