The synthesis, structure, magnetic and Mössbauer spectral properties of an Fe–Zr carboxylate–alkoxide derivative containing an {Fe2Zr2(μ3-O)2} core

Abstract

Reaction of [Fe₃(μ₃-O)(O₂CPh)₆(H₂O)₃](O₂CPh) with pyridine yields a product (2) which on recrystallisation rearranges to [Fe₆(μ-O)₂(μ-OH)₂(O₂CPh)₁₂(py)₂] (3). Magnetic and Mössbauer spectral analyses suggest that compound (2) contains an Fe₄(O)₂ cluster. The unrecrystallised material (2) reacts with Zr(OBu^t)₄ to form [Fe₂Zr₂(μ₃-O)₂(μ-O₂CPh)₆(OBu^t)₄(py)₂] (4). The mixed metal cluster has a “butterfly” configuration with Fe^III atoms coordinated by pyridine forming the “body” position. It displays weak antiferromagnetic behaviour, closely modelled as an Fe₂O₂ dimer with g = 2.01 and J = −1.42 cm⁻¹. Its Mössbauer spectrum has the high-spin Fe(III) parameters δ = 0.51 mm s⁻¹ and ΔE_Q = 0.65 mm s⁻¹ at 5 K. The molecular species [Zr₃(μ₃-O)(μ-O₂CPh)₂(μ-OBu^t)₂(OBu^t)₆] (5) is also detected in the reaction when excess Zr(OBu^t)₄ is present.