Synthesis,Structure Characterization And Catalytic Oxidation Of Ruthenium Carbonyl Clusters Based On Pyridylethanol Ligands

Since transition metals are widely used in catalytic oxidation reactions and exhibit good activity,the rich structure and wide variation of metal ruthenium compounds have attracted many chemists to conduct in-depth research.There are few reports in the literatures using pyridine alcohol-based ruthenium carbonyl clusters for catalytic oxidation reactions.Therefore,the Ru₃（CO）₁₂ with good stability was selected as a precursor to react with pyridine ethanol derivatives,and a series of novel pyridine oxime carbonyl hydride clusters were isolated and used for catalytic oxidation reaction.The content of this paper includes the following three parts:（1）A series of 6-methylpyridine ethanol derivatives L¹H-L¹¹H with different substituents were synthesized,and then reacted with Ru₃（CO）₁₂ in THF to separate seven kinds of diligand trinuclear ruthenium carbonyl clusters[6-CH₃PyCH₂CHRO]₂Ru₃（CO）₈[R=Ph（1a）;R=4-CH₃C₆H₄（1b）;R=4-OCH₃C₆H₄（1c）;R=4-ClC₆H₄（1d）;R=4-BrC₆H₄（1e）;R=4-CF₃C₆H₄（1f）;R=2-BrC₆H₄（1g）]and four monoligand trinuclear ruthenium carbonyl clusters[6-CH₃PyCH₂CR¹R²O]Ru₃（CO）₉[R¹=H,R²=2-OCH₃C₆H₄（2a）;R¹=H,R²=2-CF₃C₆H₄（2b）;R¹=CH₃,R²=CH₃（2c）;R¹=H,R²=2,6-（OCH₃）₂C₆H₃（2d）].The structures of the complexes were further characterized by NMR,IR,elemental analysis,and X-ray single crystal diffraction.The analysis indicated that the two-molecular ligands of the clusters 1a-1g were simultaneously co-ordinated to two Ru atoms withμ₂-O atom behaving as a three-electron donor.Each pyridine N atom is coordinated to a Ru atom to chelate two stable six-membered ring structures.The synthesized clusters have the advantages of novel structure,stable performance and simple operation.（2）The oxidation of alcohol catalyzed by the bidentate ligand Ru carbonyl clusters 1a-1g with NMO（N-methyl-N-oxidized morpholine）as an oxidant were investigated in detail.It was found that 1a-1g showed good catalytic activity in the catalytic alcohol oxidation reaction,and the catalytic activity of ruthenium cluster 1c was the best.At the same time,the catalytic system shows good catalytic activity for both aromatic and aliphatic primary alcohols and secondary alcohols,and onversion rate up to 80-96%.Finally,the mechanism of catalytic oxidation reaction is also discussed.（3）The selective oxidation of saturated C-H bonds catalyzed by the single ligand Ru carbonyl clusters 2a-2d with TBHP（tert-butanol hydrogen peroxide）as an oxidant were investigated in detail.It was found that 2a-2d showed good catalytic activity in oxidation reaction,and the catalytic activity of ruthenium cluster 2a was the best.At the same time,the catalytic system shows good catalytic activity for both aromatic and aliphatic alkanes,and onversion rate up to 80-96%.Finally,the mechanism of catalytic oxidation reaction was discussed.