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

Two novel ReIV compounds of formulae [H2bpy][ReIVCl4(ox)] (1) and [H3biim]2[ReIVCl4(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 P1&cmb.macr; . The ReIV 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 ReIV-Cl...Cl-ReIV contacts, Cl... pi type interactions and hydrogen bonds are present in the crystal lattice of both compounds, generating novel supramolecular structures based on the highly anisotropic [ReIVCl4(ox)]2- species. Examination of the magnetic properties of 1 and 2 reveals significant antiferromagnetic coupling between ReIV ions propagated primarily through the ReIV-Cl...Cl-ReIV interactions, as evidenced by the occurrence of maxima in the magnetic susceptibility at ca. 12 (1) and 17 K (2).