Heterometallic complexes involving iron(ii) and rhenium(vii) centers connected by μ-oxido bridges

Abstract

The reaction of FeI₂ with two equivalents of AgReO₄ in acetonitrile leads to yellow, crystalline Fe(ReO₄)₂(CH₃CN)₃ (1), and the treatment of 1 with four equivalents of CpFe(CO)₂CN gives orange, crystalline Fe(ReO₄)₂[CpFe(CO)₂(CN)]₄ (2). Compound 2 can also be prepared in one step by the reaction of FeI₂, AgReO₄ and CpFe(CO)₂CN in dichloromethane. The structure of 1 consists of infinite chains in which alternating {Fe(CH₃CN)₄} and {Fe(ReO₄)₂(CH₃CN)₂} units are linked by perrhenate anions to form a (–ReO₂–O–Fe(ReO₄)₂(CH₃CN)₂–O–ReO₂–O–Fe(CH₃CN)₄–O–)_n molecular wire. The structure of 2 shows a monomeric iron complex with a slightly distorted octahedral coordination environment consisting of four organometallic complexes coordinated in the equatorial plane via the cyanide groups and two monodentate perrhenates in the corresponding apical positions. Both compounds were further characterised in the solid state by IR spectroscopy, thermogravimetric analysis and magnetic susceptibility measurements. The magnetic data indicate that 1 behaves as a ferrimagnetic chain with 3D ordering below 8 K due to inter-chain interactions. Compound 2 has antiferromagnetic interactions within the Fe(ReO₄)₂[CpFe(CO)₂(CN)]₄ clusters.