Self-assembly of the tetrachlorido(oxalato)rhenate(iv) anion with protonated organic cations: X-ray structures and magnetic properties

Abstract

Two novel Re^IV compounds of formulae [H₂bpy][Re^IVCl₄(ox)] (1) and [H₃biim]₂[Re^IVCl₄(ox)] (2) [H₂bpy²⁺ = 4,4′-bipyridinium dication, H₃biim⁺ = 2,2′-biimidazolium monocation, and ox²⁻ = oxalate dianion] have been synthesised and magneto-structurally characterised. 1 crystallises in the monoclinic system with space group C2/c, and 2 crystallises in the triclinic system with space group P. The Re^IV ion in 1 and 2 is six-coordinate, bonded to four chloride ions and two oxalate-oxygen atoms in a distorted octahedral geometry. Short intermolecular Re^IV–Cl⋯Cl–Re^IV contacts, Cl⋯π type interactions and hydrogen bonds are present in the crystal lattice of both compounds, generating novel supramolecular structures based on the highly anisotropic [Re^IVCl₄(ox)]²⁻ species. Examination of the magnetic properties of 1 and 2 reveals significant antiferromagnetic coupling between Re^IV ions propagated primarily through the Re^IV–Cl⋯Cl–Re^IV interactions, as evidenced by the occurrence of maxima in the magnetic susceptibility at ca. 12 (1) and 17 K (2).