Metal-catalysed dehalogenations

It would be instructive to apply electron spin resonance spectroscopy in these various metal cation oxidations. Certainly the homogeneous nature of these reactions offers greater possibilities to the kineticist than is afforded by the heterogeneous nature of the metal-catalysed eliminations. Considering the recent discoveries of the synthetic utility of thallium in organic synthesis " , thallous salts might prove to be extremely useful catalysts for dehalogenations. as under the reaction conditions the less stable olefins are rapidly isomerised. 

As indicated in Chapter 8, the production of alkanes, as by-products, frequently accompanies the two-phase metal carbonyl promoted carbonylation of haloalkanes. In the case of the cobalt carbonyl mediated reactions, it has been assumed that both the reductive dehalogenation reactions and the carbonylation reactions proceed via a common initial nucleophilic substitution reaction and that a base-catalysed anionic (or radical) cleavage of the metal-alkyl bond is in competition with the carbonylation step [l]. Although such a mechanism is not entirely satisfactory, there is no evidence for any other intermediate metal carbonyl species. 

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