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(η5-C5H5)L]+ (L = CH3CN, CO), or [Ru(η6-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 β 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(η6-C6H6)(1a)]PF6, 4a, have been confirmed by X-ray diffraction studies.N,N'-双齿配体芳基-吡啶-2-基甲胺（aryl-pyridin-2-ylmethyl-amine）通式为ArNH-CH₂-2-C₅H₄N（记为配体1），其中Ar分别为4-甲基苯基（4-CH₃-C₆H₄，1a）、4-甲氧基苯基（4-CH₃O-C₆H₄，1b）、2,6-二甲基苯基（2,6-(CH₃)₂-C₆H₃，1c）与4-三氟甲基苯基（4-CF₃-C₆H₄，1d）。该类配体可与[Ru(联吡啶(bipy))₂]²+、[Ru(η⁵-环戊二烯基)L]+（L为乙腈CH₃CN、一氧化碳CO）或[Ru(η⁶-芳烃)Cl]²+（芳烃为苯benzene、对伞花烃p-cymene）发生配位反应，该过程具有非对映选择性或非对映专一性。本研究包含对上述新型配合物的详细立体化学分析。在碱催化条件下，这些仲胺配体经配位后可被分子氧氧化为亚胺，反应副产物为过氧化氢（hydrogen peroxide）；在循环伏安法（cyclic voltammetry）测试的实验条件下，同样可观测到胺到亚胺的氧化过程。对配位后的胺配体进行去质子化时，仅当配体为(1-甲基-1-吡啶-2-基乙基)-对甲苯基胺（1e）时可得到可分离的酰胺配合物，该配体的N-H键β位不含氢原子。通过X射线衍射（X-ray diffraction）实验确认了以下配合物的晶体结构：[Ru(2,2'-联吡啶)₂(1b)](PF₆)₂（2b）、[Ru(2,2'-联吡啶)₂(1c)](PF₆)₂（2c）、trans-[RuCl₂(COD)(1a)]（3）以及[RuCl₂(η⁶-苯)(1a)]PF₆（4a）。