ABSTRACT An air‐ and moisture‐stable ruthenium(II) complex, trans ‐Ru(H 2 L)H(CO)(PPh 3 ) 2 PF 6 , has been synthesized using a redox‐active bidentate 2‐(pyridylazo)aniline (H 2 L) ligand. The complex was comprehensively characterized by spectroscopic techniques, single‐crystal x‐ray diffraction (SCXRD), and high‐resolution mass spectrometry, while its electronic and redox features were further probed through cyclic voltammetry and density functional theory (DFT) studies. Catalytically, it promotes the efficient dehydrogenation of primary alcohols followed by their tandem coupling with indoles to afford bis(indolyl)methanes, including pharmacologically relevant derivatives. Mechanistic investigations highlight the crucial role of the redox‐active azo unit as the primary electron reservoir, with the Ru(II) center functioning predominantly as a redox spectator. This catalytic strategy offers key advantages such as facile synthesis, low catalyst loading, broad substrate scope (75 examples), shorter reaction times and mild reaction conditions, collectively emphasizing the promise of azo‐based ligands in advancing Ru(II)‐catalyzed sustainable transformations.
Naskar et al. (Wed,) studied this question.