Photodecomposition of dichloromethane catalyzed by tetrachloroferrate(III) supported on a Dowex anion exchange resin.

The FeCl4(-) ion, heterogenized on a Dowex ion exchange resin, catalyzes the aerobic photodecomposition of neat CH2Cl2. Phosgene production was used to characterize the extent of decomposition, although it appears to be a secondary product from the decomposition of chloroform, which is suggested to arise from the reaction of dichloromethanol with hydrogen chloride. The yield of CHCl3 increases when the production of phosgene is suppressed by water or acetonitrile. CuCl4(2-), likewise heterogenized on Dowex, is photocatalytically inactive.