Halocarbon complexes

By definition enzymes that are able to oxidize chloride, bromide, and iodide are called chloroperoxidases and those able to oxidize bromide and iodide, bromoperoxidases. If a nucleophilic acceptor (RH) is present, a reaction will occur with HOX and halogenated compounds see Halocarbons Halocarbon Complexes) are produced (equation 2). 

In the earliest authentic halocarbon complex (1982), o-diiodobenzene was found to chelate to cationic Ir(III) as shown in diagram (5)." An earlier proposed example proved to be misidentified when the crystal structure was carried out. To be stable, any such complex must resist oxidative addition, hence the use of an oxidation state, Ir(III), that is only oxidized with difficulty. The normally rather weakly basic halocarbon lone pairs are often reluctant to bind, but chelation and involvement of the least electronegative hahde, iodine, favor binding as does the cationic character of the complex. A series of such complexes was soon found, including complexes of fr(I)" and a series of weakly bound dichloromethane complexes for certain systems." These solvento complexes can be very labile and so find use as precursors for binding of other weakly basic hgands. Even fluorocarbon complexes proved viable." A review of the area is available. It now seems... 

The overall photoreaction rate of a given halocarbon in a certain aquatic environment is the sum of the rates of the direct photoreactions of the uncom-plexed halocarbon, indirect photoreactions involving reactive transients that are produced by natural substances, and photoreactions of halocarbon complexes. After first discussing the effects of sorption on photoreaction kinetics, we then discuss these various reaction pathways in more detail. 

---