Reduction of nitrosoarene ligands in binuclear palladium(ii) complexes

Reduction of the binuclear Pd^II complexes Pd₂(OCOR)₂(o-CH₂C₆H₄—NO)₂ (1) and Pd₂(OCOR)₂(o-PhN—C₆H₄—NO)₂ (2) (where R = Me, CF₃, Bu^t, or Ph) by sodium borohydride, an ethanolic solution of KOH, or molecular hydrogen was examined. The first stage of reduction was demonstrated to afford metallic palladium and aromatic amines, viz., o-toluidine o-Me—C₆H₄—NH₂ from complex 1 and aniline Ph—NH₂ from complex 2. The reactions with molecular hydrogen involve deeper stages to yield cyclic ketones (o-methylcyclohexanone and cyclohexanone) and then cycloalkanes (methylcyclohexane and cyclohexane, respectively). The latter reactions are accompanied by elimination of N₂. The mechanism of reduction of complexes 1 and 2 with molecular hydrogen was proposed.