A tetragonal core with asymmetric iron environments supported solely by bis(mu-OH){mu-(O-H center dot center dot center dot O)} bridging and terminal pyridine amide (N, O) coordination: A new member of the tetrairon(III) family

摘要

Room-temperature aerobic reaction of [Fe(MeCN)(4)][ClO4](2) with 1,3-bis(2-pyridinecarboxamido)propane (H(2)bpp) yields the tetrairon(III) complex [Fe-4(H(2)bpp)(4)(mu-OH)(2)(mu-OHO)]-[ClO4](7)center dot 2H(2)O.xMeCN (1 center dot xMeCN, 0 <= x <= 3). Crystal structure determination reveals that 1 center dot 3MeCN is a new member of the tetrairon(III) family, bridged solely by two hydroxido ligands and a localized {O-H center dot center dot center dot O}(3-) bridging unit. The properties of the "tetragonal" core [Fe-4(mu-OH)(2){mu-(O-H center dot center dot center dot O)}](7+) have been investigated by variable-temperature magnetic and Mossbauer spectroscopic measurements. Successful modeling of the data has revealed asymmetric iron environments and three types of magnetic exchange interactions [through mu-OH and mu-O/mu-OH of mu-(O-H center dot center dot center dot O) bridges]. This tetragonal core is a valuable addition to the tetrairon(III) cluster family from inorganic and bioinorganic perspectives. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008).