Also known as reductive Friedel–Crafts reaction, the Fischer–Hafner synthesis entails treatment of metal chlorides with arenes in the presence of aluminium trichloride and aluminium metal.  The method was demonstrated in the 1950s with the synthesis of bis(benzene)chromium by Walter Hafner and his advisor E. O. Fischer.  The method has been extended to other metals, e.g. [Ru(CMe)].  In this reaction, the AlCl serves to remove chloride from the metal precursor, and the Al metal functions as the reductant.  The Fischer-Hafner synthesis is limited to arenes lacking sensitive functional groups.