Synthesis, crystal structure and catalytic properties of (p-cymene)ruthenium(II) azophenol complexes: azophenyl to azophenol conversion by oxygen insertion to a ruthenium-carbon bond

Azophenol complexes of formulation [(eta (6)-p-cymene)RuCl(L-n)] (1-6, n = 1-6) were prepared by two synthetic methods involving either an oxygen inse rtion to the Ru-C bond in cycloruthenated precursors forming complexes I an d 2 or from the reaction of [{(eta (6)-p-cymene)RuCl}(2)(mu -Cl)(2)] with a zophenol ligands (HL3-HL6) in the presence of sodium carbonate in CH2Cl2, T he molecular structure of the 1-(phenylazo)-2-naphthol complex has been det ermined by X-ray crystallography. The complex has a eta (6)-p-cymene group, a chloride and a bidentate N,O-donor azophenol ligand. The complexes have been characterized from NMR spectral data. The catalytic activity of the co mplexes has been studied for the conversion of acetophenone to the correspo nding alcohol in the presence of KOH and isopropanol. Complexes 4 and 6 hav ing a methoxy group attached to the ortho-position of the phenylazo moiety and 2 with a methyl group in the meta-position of the phenolic moiety show high percentage conversion (> 84%). (C) 2001 Elsevier Science B.V. All righ ts reserved.