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

Abstract

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(eta5-C5H5)L]+ (L = CH3CN, CO), or [Ru(eta6-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(eta6-C6H6)(1a)]PF6, 4a, have been confirmed by X-ray diffraction studies.

Olefin oligomerization, homopolymerization and copolymerization by late transition metals supported by (imino)pyridine ligands

“…Deprotonation of the ketimine group on highly conjugated iminopyridyl systems by strong non-nucleophilic bases, such as Me 3 SiCH 2 Li or MeLi, followed by aqueous quenching, gives vinylaniline derivatives in almost quantitative yields (Scheme 7a) [46]. Nucleophilic attack of MeLi at the imine carbon of unsubstituted iminopyridyl ligands has been reported by Garcia-Herbosa and co-workers (Scheme 7b) [47]. The treatment with an excess of aluminum alkyls (Me 3 Al or Et 3 Al), followed by hydrolysis, results in the complete reductive alkylation of the imine double bond (Scheme 7c) [48].…”

“…The synthesis of late transition metal catalyst precursors (mostly from the first transition row) is a straightforward process, which involves the plain addition of the solid ligands to n-BuOH, THF, toluene or CH 2 Cl 2 solutions of either anhydrous or hydrated dihalides (Scheme 8) [1,2,[9][10][11][12]14,15,20,21,25,26,32,33,37,38,[47][48][49]53,54]. Irrespective of the metal, the dihalides are sparingly soluble in aromatic hydrocarbons, while they dissolve fairly well in polar solvents.…”

Catalytic oxidation of primary aromatic alcohols using half sandwich Ir(III), Rh(III) and Ru(II) complexes: A practical and theoretical study

“…The N, N' bidentate ligand precursor N-(pyridin-2-ylmethylene)aniline and metal complexes of iridium, rhodium and ruthenium were synthesised according to methods discussed elsewhere [39][40][41]. The structure and purity of the synthesized metal complexes, along with the ligands were confirmed by single crystal XRD, NMR, IR and electronic absorption spectral studies.…”

Ruthenium(II) complex catalysts bearing a pyridyl-supported pyrazolyl-imine ligand for transfer hydrogenation of ketones

“…During the purification of 9 by flash silica gel column chromatography in air, transformation of yellow 9 to purple 8a was always accompanied that pure complex 9 could not be obtained. It has been known that cationic and pincer-type Ru(II) amine complexes can be oxidized to Ru(II) imino complexes by oxygen [30,31]. Complex 8a is bestowed with a poor solubility in organic solvents and its satisfied 13 C{ 1 H} NMR spectrum was not successfully collected.…”