Reduction of Organic Halogen Compounds

The Co(bipy)3+ ion is a useful catalyst for a number of borohydride reductions, e.g., organic nitro compounds are reduced smoothly to amines at pH 6.5-7 the true reducing agent is Co(bipy)3+. The oxidation-reduction potential for Co(I)/Co(II) is 0.91 volt (vs. standard calomel electrode in 50% aqueous ethanol) and this should fall between the potentials of the other reactants (709). Catalytic reductions of organic halogen compounds may be achieved (436), and the system is reactive to small molecules such as NgO (38). 

Preparation. Diborane is generally made by treatment of sodium borohydride with boron trifluoride etherate. During a study of the reduction of organic halogen compounds with sodium borohydride, Bell et al. noted that the stoichiometry results in generation of diborane (as monomer) ... 

Reduction of alkyl or aryl halides. Reduction of organic halogen compounds by sodium borohydride proceeds more rapidly in DMSO than in anhydrous diglyme.8... 

An amalgam reduction of a halogen compound may result in cleavage of the carbon-halogen bond, a coupling reaction, a reductive elimination, or formation of an organic mercury compound. 

Use Preparation of hydrogen, reduction of metal halogen compounds and organic compounds, reagent in analytical chemistry. 

In this part of the chapter, the discussion is focused on the direct cathodic reduction of halogenated organic compounds, although the last section will address the increasingly active area of catalytic reductions of carbon-halogen bonds. 

The use of nickel-aluminum alloy in aqueous alkali for the reduction of organic compounds has been observed (60c) to bring about the displacement by hydrogen of methoxy, halogen, and sulfonic acid groups from several types of benzenoid compounds. Table III summarizes the... 

Mazur DJ, Weinberg NL (1987) Methods for the electrochemical reduction of halogenated organic compounds, US, US 4,702,804 Chem Abstr 108 (1988) 175949s... 

In this section, we discuss processes in which cobalt-containing catalysts are employed for a variety of applications such as the reductions of molecular oxygen, carbon dioxide, and halogenated organic compounds as well as the oxidation of hydrazine. 

In a fashion similar to that of cobalt salen, distinct redox chemistry can be observed for each of the two cobalt centers of (28). Coulometric studies showed that the complex can undergo a one-electron reduction as well as a one-electron oxidation of each cobalt center and that there is no interaction between those cobalt centers. Thus, the two metal centers can be used as separate catalytic sites for the reduction of halogenated organic compounds. In the same article [147] is a hst of literature citations of work done over the past 20 years by the group of Hisaeda on the catalytic behavior of electroreduced vitamin B12 derivatives. 

The reductions of halogenated organic compounds (RX) involve the cleavage of carbon-halogen bonds [62]. Depending on the solvent, supporting electrolyte, electrode material and potential, it is possible to electrogenerate either alkyl radicals (R ) or carbanions (R ), which then can lead to the fonnation of dimers (R-R), alkanes (RH) and olefins [R(-H)] ... 

---