Structure, electrochemistry, spectroscopy, and magnetic resonance, including high-field EPR, of {(μ-abpy)[Re(CO)3X]2}o/•−, where abpy = 2,2′-azobispyridine and X = F, Cl, Br, I

Attempts to prepare and study the title complexes yielded the structurally characterized neutral compounds anti-{(μ-abpy)[Re(CO)3X]2}, X = Br (I41/a), I (C2/c), and two crystalline forms of anti-{(μ-abpy)[Re(CO)3Cl]2}. One of these forms (P21/c) has been reported before, the other (I41/a), obtained through crystallization in the presence of Zn, is isostructural to the form found for anti-{(μ-abpy)[Re(CO)3Br]2}. Syntheses of {(μ-abpy)[Re(CO)3Cl]2} at high or low temperatures yielded different compositions, the high temperature procedure led to partial formation of syn/anti mixtures and one-electron reduced species. The same was observed to a greater extent in the preparation of labile syn/anti-{(μ-abpy)[Re(CO)3F]2}o/•−. The identity of isolated species was investigated using 1H NMR spectroscopy, variable frequency EPR spectroscopy, cyclic voltammetry, UV/Vis- and IR-spectroelectrochemistry. The effects of halide variation on structure, reduction potentials, isomerism and electronic situation are being discussed.