Magneto-structural study on a series of rhenium(IV) complexes containing biimH2, pyim and bipy ligands

Three rhenium(IV) mononuclear compounds of formulae [ReCl4(biimH(2))]. 2DMF (1), [ReCl4(pyim)].DMF (2) and [ReCl4(bipy)] (3) (biimH(2) = 2,2'-biimidazole, pyim = 2-(2'-pyridyl)imidazole, bipy = 2,2'-bipyridine and DMF = N,N-dimethylformamide) have been prepared and characterized. The crystal structure of 2 was determined by single crystal X-ray diffraction. Compound 2 crystallizes in the monoclinic system with P2(1)/c as space group. The rhenium atom is six-coordinated by four Cl atoms and two nitrogen atoms from a bidentate pyim ligand [average values of Re-Cl and Re-N bonds lengths being 2.330(2) and 2.117(4) angstrom, respectively]. The magnetic properties were investigated from susceptibility measurements performed on polycrystalline samples of 1-3 in the temperature range 1.9-300 K. The magnetic behaviour found is typical of antiferromagnetically coupled systems, and they,exhibit susceptibility maxima at 2.8 (1 and 2) and 5.6 K (3). Short Re-IV-Cl...Cl-Re-IV contacts through space account for the antiferromagnetic behaviour observed.