Idealized equations for the synthesis are:: CrCl3 + 2/3 Al + AlCl3 + 2 C6H6 → [Cr(C6H6)2]AlCl4 + 2/3 AlCl3: + 1/2 Na2S2O4 → [Cr(C6H6)2 + NaAlCl4 + SO2==Structure elucidation==Compounds closely related to had been prepared many years before Fischer's work by Franz Hein by the reaction of phenylmagnesium bromide and CrCl3.