Catalytic reductive homocoupling of 9-bromofluorene

A number of organometallic compounds and inorganic salts, including the group 8 metal carbonyls M3(CO)12 and salts MCl3 (M = Fe, Ru, Os), were tested for their catalytic activity in the reductive coupling of 9-bromofluorene. Among them, FeCl3 was found to show excellent activity (TOF = 1960). The reaction is believed to proceed via a radical mechanism.