Metal Ions as Reductants

Two parallel paths have been identified in the reduction of monochloro- and dichloro-acetic acids by uranium(iii). The reactions have been studied in various binary alcohol-water mixtures as well as in aqueous media. Under the latter conditions the rate may be described by 

El-Wakil, and J. Vepfek-Sigka, Coll Czech. Chem. Comm., 1978,43,3306. 

Preferential reaction thus appears to take place via metal dimers in both systems. 

Ligand transfer has been suggested as the initial step in the reduction of aromatic aldehydes by Cr in acid solution.  

The reaction of nitrosylpenta-ammineruthenium(ii) with RNH2 (R=Me or Et) may be written as 

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Cyano-de-diazoniations of the Sandmeyer type have been used for the synthesis of aromatic nitriles for many decades (example Clarke and Reed, 1964), as cyanide ions are comparable to bromide and iodide in many respects. A homolytic cyano-de-diazo-niation that does not use metal ions as reductant or ligand transfer reagent was described by Petrillo et al. (1987). They showed that substituted diazosulfides (XC6H4 — N2 — SC6H5), either isolated or generated in situ from arenediazonium tetrafluoroborates and sodium benzenethiolate, react with tetrabutylammonium cyanide in dimethylsulfoxide under photon stimulation, leading to nitriles (XC6H4CN). The method worked well with eleven benzenediazonium ions substituted in the 3- or 4-position, and was also used for the synthesis of phthalo-, isophthalo-, and tere-... 

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