The synthesis relies on the oxidation of Iron(II) to Iron(III). The intermediate ferrous oxalate is insoluble, which allows for its purification before the coordination step. The hydrogen peroxide serves as a potent oxidizing agent in the acidic environment provided by oxalic acid. The final complex is photosensitive; Iron(III) oxalate complexes can undergo photoreduction back to Iron(II), explaining why the compound must be stored in the dark.