Synthesis, crystal structure, electrochemical and magnetic properties of (NBu4)[ReCl5(L)] with L = pyrimidine and pyridazine

Two novel rhenium(IV) compounds, namely (NBu4)[ReCl5(pym)] (1) and (NBu4)[ReCl5(pyd)] (2) (pym = pyrimidine, pyd = pyridazine and NBu4 = n-tetrabutylammonium cation), have been obtained by reaction of [ReCl6](2-) and the diazine in dmf, and their crystal structures determined by single-crystal X-ray diffraction. The structures of 1 and 2 consist of [ReCl5(pym)](-) or [ReCl5(pyd)](-) anions and NBu4+ cations held together by electrostatic forces and van der Waals interactions. Stacking interactions are present only in 1. The coordination sphere of the Re-IV ion is defined by five chloride anions and one nitrogen atom of a monodentate diazine, resulting in a distorted octahedral environment. Voltarnmetric profiles in CH3CN show a one-electron reduction step at ca. -0.5 V vs. NHE for both complexes. Magnetic measurements reveal weak antiferromagnetic interactions among the metal centers in the crystal lattices of 1 and 2, superimposed to the well-known zero-field splitting of Re(IV) compounds.