Oxidation of Re(V) to Re(VII) in Conjugated Metallacycles

The metal center of metallacycles can adopt different oxidation states, which would result in the change of structure and property. In this work, metallabenzofuran complexes with a Re(V) center are obtained from the reaction of ReOCl 3 (PPh 3 ) 2 with o ‐ethynyl phenols. Further oxidation of these Re(V)‐metallacycles produces Re(VII)‐metallabenzofurans as rare examples of high valent conjugated d 0 ‐metallacycles of late transition metals. Although they have a delocalized five‐membered rhenafuran structure, density functional theory studies show that these Re(V)‐ and Re(VII)‐metallacycles are nonaromatic.