Synthesis,Characterization And Catalytic Oxidation Of Alcohol By Ruthenium And Rhenlecarbonyl Complexes Containing Pyridine Methanol Ligand

Pyridine is a very important kind of heterocyclic organic ligands,which has strong coordination ability so pyridine can form strong chemical bonds with kinds of transition metals.Although 2-pyridine methanol is a relatively simple derivative of pyridine,it has the advantages of having more coordination points and easy structural modification.Moreover,different substituents carried in 2-pyridinemethanol may have a certain impact on the catalytic reaction.Although the pyridine-methanol ligand complex structure varied,reports about the synthesis of pyridinemethanol carbonyl complexes are extremely rare.In this paper,the reactivity of 2-pyridinemethanol with Ru₃?CO?₁₂ and Re₂?CO?₁₀ was studied,ten trinuclear ruthenium complexes and eight rhenium carbonyl complexes were isolated and characterized.The catalytic activities of these two complexes for secondary alcohol oxidation were also investigated.The details are as follows:1.The reactivity of 2-pyridinemethanol derivatives with Ru₃?CO?₁₂ was studied.Ten trinuclear ruthenium carbonyl complexes[?-?²-2-?C₅H₄N?C?CH₂?₄?O?]₂Ru₃?CO?₈?2a?,[?-?²-2-?C₅H₄N?C?CH₂?₅?O?]₂Ru₃?CO?₈?2b?and[?-?²-2-?C₅H₄N?C?O??R¹??R²?]₂Ru₃?CO?₈[R¹=CH₃,R²=CH₃?2c?;R¹=CH₃,R²=C₆H₅?2d?;R¹=H,R²=C₆H₅?2e?;R¹=H,R²=4-CH₃C₆H₄?2f?;R¹=H,R²=4-OMeC₆H₄?2g?;R¹=H,R²=4-ClC₆H₄?2h?;R¹=H,R²=4-BrC₆H₄?2i?;R¹=H,R²=4-CF₃C₆H₄?2j?]were separated.The results were characterized by NMR,IR and elemental analysis.The six crystals obtained were characterized by X-ray single crystal diffraction.Two pyridine methanol ligands are coordinated with two Ru atoms via?₂-O bridge of a three-electron donor in the complex.Each N atom of pyridine is coordinated with one Ru atom,therefore,the complex forming two five-membered rings in the structure.2.The reactivity of 2-pyridinemethanol derivatives with Re₂?CO?₁₀ was studied.Eight trinuclear rhenium carbonyl complexes[?-?-2-?C₅H₄N?C?CH₂?₄?O?]₂Re₂?CO?₆?3a?,[?-?-2-?C₅H₄N?C?O??R¹??R²?]₂Re₂?CO?₆[R¹=CH₃,R²=C₆H₅?3b?;R¹=H,R²=C₆H₅?3c?;R¹=H,R²=4-CH₃C₆H₄?3d?;R¹=H,R²=4-OMeC₆H₄?3e?;R¹=H,R²=4-ClC₆H₄?3f?;R¹=H,R²=4-BrC₆H₄?3g?;R¹=H,R²=4-CF₃C₆H₄?3h?]were separated.The results were characterized by NMR,IR and elemental analysis.The three crystals obtained were characterized by X-ray single crystal diffraction.The O of hydroxyl groups of the two pyridinemethanol ligands coordinate to two Re atoms simultaneously.Each N atom of pyridine is coordinated to a Re atom to chelate to form two five-membered ring structures.3.The reactions of the complexes 2a-2j for the secondary alcohol oxidation were studied.The results show all of catalytic yields arriving 80%,2e?R=C₆H₅?>2h?R=4-ClC₆H₅?2i?R=4-BrC₆H₅?>2j?R=4-CF₃C₆H₅?>2a?R=cyclopentyl?>2b?R=cyclohexyl?>2c?R=?Me?₂?>2g?R=4-OMeC₆H₅?>2d?R=C₆H₅,Me?>2f?R=4-MeC₆H₅?.Moreover,the yield of electron-donating substrate is slightly higher than the yield of electron-drawing substrate.4.The reactions of the complexes 3a-3h for the secondary alcohol oxidation were studied.The results show that the catalytic activity of these complexes is very well,the highest catalytic yield reached only 54%.In comparison,complexes with electron-donating groups have a slightly higher catalytic yield.