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.

Graphical abstractReduction to persistent radical anion complexes and further to labile dianions as well as the isomerization from isolated anti to syn forms is facilitated for the compounds (μ-abpy)[Re(CO)3X]2 on going from X = I via Br and Cl to F.Figure optionsDownload full-size imageDownload as PowerPoint slide