Novel examples of simultaneous reductive azo cleavage and oxidative aromatic ring amination in rhodium complexes of 2-(Arylazo)pyridine

Abstract

The reaction of [AgL¹₂]ClO₄ (L¹=NH₄C₅N=NC₆H₄(R)) with [RhCl₂L¹²]ClO₄ (1) in boiling ethanol affords green complexes of the type [RhClL¹L²](ClO₄) (2; L²=NH₄C₅N=NC₆H₃(R)NC₅H₄N). This reaction is an unprecedented example wherein the anionic tridentate N,N,N donor L² is formed by the fusion of the pyridyl imide fragment [PyN]^2- to a pendant aromatic ring of the coordinated ligand L¹. The [PyN]^2- originates from the splitting of a diaza function of coordinated L¹. The complexes have been fully characterized, and structures of the two representative complexes 1a and 2a (R=H) are reported. A reaction pathway based on the reduction potentials of the coordinated ligand L¹ is proposed for the above transformation.