The molecular and electronic structure of the asymmetric, trinuclear complex [LFeIII(mu-O) (mu-piv)(2)Fe-III(mu-OH)(mu-piv)(2)Fe-III-(piv)(2)]center dot C6H5CH3 (L=1,4,7-trimethyl-1,4,7-triazacyclononane, piv = pivalate(1-))

The synthesis and molecular structure as determined by single-crystal X-ray crystallography of the neutral complex [LFeIII(mu-O)(mu-piv)(2)Fe-III(mu-O H)(mu-piv)(2)Fe-III(piv)(2)]. C6H5CH3 (1) are described (L = 1,4,7-trimethy l-1,4,7-triazacyclononane; piv = pivalate(1-)). The electronic structure of 1 has been established by temperature-dependent susceptibility measurement s (2-295 K), W-Vis, EPR, and Mossbauer 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 = -2JS(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-fie ld Mossbauer spectroscopy. (C) 1999 Elsevier Science S.A. All rights reserv ed.