Arylazo oximes

The electronic and IR spectra of [Rh(N02)6] are consistent with the expected RhNg chromo-phore, and while ligand field bands were not observed, CT absorbances occur at 317 and 275 nm. Arylazo oximes (N—N) form [Rh(N—N)j] complexes with Rh in which the arylazo oxime acts as a bidentate ligand (five-membered rings 57). Reaction of Rh(N03)3-3H20 with the appropriate arylazo oxime in ethanol at pH 4 (with CO," used to adjust pH) leads to a precipitate offac-and ier-[Rh(N—N),]. The geometric isomers can be separated on alumina, and H NMR showed that approximately equivalent amounts of the fac and mer isomers formed (for R = Me or Pr and Ar = Ph). This represents an unexpected (and unexplained) enhancement of the population of the fac isomer, as statistically, a fac/mer ratio of 1 /3 would be expected only the mer form was detected for [Co(N—N)3]. These rhodium complexes all display intense absorption bands near 480 and 320 nm, which are presumed to be intraligand bands. ... 

Cis and trans isomers of arylazo oximato platinum complexes have been isolated. Trans to cis isomerization can be achieved simply by heating in hydrocarbon or alcohol solvents, and the reverse step is performed by treating the cis complex with hydrogen chloride, followed by neutralization (Scheme 6). Hydrogen chloride opens the arylazo oximate ring, but the intimate nature of the site exchange has not yet been elucidated. 

Amino-5-imino-3-pyrazolidinones have been synthesized by reduction of the corresponding oximes.644,1339 Such amines form ureas and thioureas by reaction with potassium cyanate in acid solution and with phenyl isothiocyanate.644 4-Arylimino-5-imino-3-pyrazolidinones have been prepared by reaction of the 5-imino-3-pyrazolidinones with p-amino-A.-AT-diethylaniline in the presence of silver salts as oxidizing agents (eq. 172).244,519,1255,1538 4-Arylazo-5-imino-3-pyrazolidinones have most frequently been prepared by reaction of 5-imino-3-pyrazoli-dinones with aryldiazonium chlorides, as is usual for the preparation of similar compounds.591,594,920,1087,1255,1339,1539,1649 One such compound has been prepared by the Curtius rearrangement of the corresponding 4-arylazo azide.594... 

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