A Tetragonal Core with Asymmetric Iron Environments Supported Solely by Bis(μ‐OH){μ‐(O–H···O)} Bridging and Terminal Pyridine Amide (N, O) Coordination: A New Member of the Tetrairon(III) Family

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