Crystal structure and magnetic properties of DI-μ-2,2,2-trifluoroethoxo-tetrakis(pentane-2,4-dionato) diiron(III)

Abstract

The X-ray crystal structure of the title compound has been determined. The crystal structure is built up of two crystallographically independent, discrete, dinuclear molecules (dimer A and B). Both centrosymmetric dimers consist of two iron(III) ions bridged by two 2,2,2-trifluoroethoxo-groups, the coordination around each iron centre is approximately octahedral. The FeO(bridge) bond lengths are in the range 2.017(3)–2.031(3) Å; the FeOFe bridging angles are 102.8(2) (dimer A) and 102.4(2)° (dimer B). The α-carbons of the bridging group are displaced on the opposite sides of the Fe2O2 bridging plane by 0.700(6) (dimer A) and 0.769(5) Å (dimer B). The magnetic susceptibility of powdered samples of [Fe(acac)2(OCH2CF3)]2 has been examined in the temperature range 4.2–292 K. The compound exhibits an antiferromagnetic exchange interaction, with the − 2J parameter equal to 13.0 cm−1. The structural and magnetic susceptibility data of the title compound was compared to those for the previously characterized [Fe(acac)2(OC2H5)]2. Differences in the magnetic properties between both compounds were assigned to differences in the chemical nature of the bridging ion and/or differences observed in the angle between the Fe2O2 bridging plane and the OC(bridge) vector.