σ-Bonded organotransition-metal ions. Part XII. Bimolecular displacement of cobalt(III) from organo-pentacyanocobaltate(III) ions and of chromium(III) from penta-aquo-organochromium(III) ions by nitrosating species

Abstract

Benzyl- and pyridiomethyl-pentacyanocobaltate(III) ions and penta-aquopyridiomethylchromium(III) ions react rapidly with nitrous acid in aqueous mineral acid to give benzaldoxime and pyridinium aldoximes, respectively. The kinetics of these reactions have been studied and both the nitrous acidium ion and nitrosyl chloride have been shown to be effective reagents. The reactions are believed to involve the bimolecular displacement of the metallic groups Co(CN)₅^2– and Cr(H₂O)₅³⁺ by attack of the nitrosating species on saturated carbon. The initial product of this reaction, the C-nitroso-compound, then rapidly rearranges to the observed oxime. The rates of these reactions are comparable with those for diazotisation of mono- and di-nitroanilines and the reaction provides a possible general method for the synthesis of oximes and hence of aldehydes, from alkyl halides.