REDUCTION BY ORGANOMETALLIC COMPLEXES
UNIVERSITY COLL DUBLIN (IRELAND)
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Solutions of azobenzene .01 M and tricarbonylarenechromiums .01 M , RC6H5CO3, in dulute ethanolic hydrochloric acid .01 M under N give fair yields up to 30 of benzidine dihydrochloride, identified by analysis and I.R. spectrum. The reaction occurs for the substituent range RMe,CL,H,NH2,NHMe and NMe2 and is facilitated by electron repelling groups this is consistent with protonation at the chromium atom being assisted by charge transfer. No reduction is observed in the absence of acid so some type of protonation seems essential. More dilute solutions .0001 M of the complexes undergo fairly rapid decomposition in ethanolic hydrochloric acid under N with the evolution of CO and formation of free arene. Spectrophotometric studies of tricarbonylanilinechromium show an immediate fall in intensity of the 3150 angstrom band corresponding to protonation at the N atom followed by a further decrease due to decomposition extrapolation gives a pKa value to 1.26. Results support the view that reduction by organometallic complexes is related to protonation at the metal atom.
- Organic Chemistry