Diastereospecific and diastereoselective syntheses of ruthenium(II) complexes using N,N′ bidentate ligands aryl-pyridin-2-ylmethyl-amine ArNH-CH2-2-C5H4N and their oxidation to imine Ligands

Coordination of N,N' bidentate ligands aryl-pyridin-2-ylmethyl-amine ArNH-CH2-2-C5H4N 1 (Ar = 4-CH3-C6H4, 1a; 4-CH3O-C6H4, 1b; 2,6-(CH3)(2)-C6H3, 1c; 4-CF3-C6H4, 1d) to the moieties [Ru(bipy)(2)](2+), [Ru(eta(5)-C5H5)L](+) (L = CH3CN, CO), or [RU(eta(6)-arene)Cl](2+) (arene = benzene, p-cymene) occurs under diastereoselective or diastereospecific conditions. Detailed stereochemical analysis of the new complexes is included. The coordination of these secondary amine ligands activates their oxidation to imines by molecular oxygen in a base-catalyzed reaction and hydrogen peroxide was detected as byproduct. The amine-to-imine oxidation was also observed under the experimental conditions of cyclic voltammetry measurements. Deprotonation of the coordinated amine ligands afforded isolatable amido complexes only for the ligand (1-methyl-1-pyridin-2-yl-ethyl)-p-tolyl-amine, 1e, which doesn't contain hydrogen atoms in a beta position relative to the N-H bond. The structures of [Ru(2,2'-bipyridine)(2)(1b)](PF6)(2), 2b; [Ru(2,2'-bipyridine)(2)(1c)](PF6)(2), 2c; trans-[RuCl2(COD)(1a)], 3; and [RuCl2(eta(6)-C6H6)(1a)]PF6, 4a, have been confirmed by X-ray diffraction studies.