Synthesis,Characterization And Catalytic Properties Of Ruthenium Carbonyl Complexes With Pyridine-Alkoxy Ligands

Organic ruthenium metal compounds are widely used in oxidation-reduction reactions because of the wide oxidation state change of ruthenium?-2 to+8?,which make ruthenium compounds have excellent redox ability and high catalytic activity.Among them,ruthenium carbonyl compounds having various structures,good stability and excellent catalytic activity are very popular.Based on the high catalytic activity and structural diversity of ruthenium carbonyl compounds,a series of novel ruthenium carbonyl clusters chelated with pyridine-alkoxide ligands were synthesized from the reaction of pyridine-alkoxide ligands with Ru₃?CO?₁₂.The ruthenium carbonyl clusters with pyridine methanol ligands were used to catalyze the oxidation reaction of alcohols and the oxidation reaction of amines to amides,and the application of ruthenium clusters in the oxidation of alcohols and amines was explored.The main results of this paper are listed as following:1.Several new trinuclear ruthenium carbonyl complexes chelated with 6-bromopyridine alcohol ligands,[6-Br-PyCR¹R²O]₂Ru₃?CO?₈{R¹=R²=CH₃?2a?;R¹=H,R²=Ph?2b?;R¹=H,R²=4-CH₃C₆H₄?2c?;R¹=H,R²=4-OCH₃C₆H₄?2d?;R¹=H,R²=4-ClC₆H₄?2e?;R¹=H,R²=4-BrC₆H₄?2f?;R¹=H,R²=4-CF₃C₆H₄?2g?;R¹=H,R²=2-OCH₃C₆H₄?2h?;R¹=H,R²=2-CF₃C₆H₄?2i?}?[6-Br-PyCR¹R²O]Ru₃?CO?₉{R¹=R²=CH₃?3a?;R¹=CH₃,R²=Ph?3j?}?[6-Br-PyC?CH₂?₄O]Ru₃?CO?₉?3k??[6-Br-PyC?CH₂?₅O]Ru₃?CO?₉?3l?,were synthesized from the reaction of Ru₃?CO?₁₂ with 6-bromopyridine alcohol ligands,respectively.The thirteen ruthenium carbonyl complexes were characterized by IR,NMR and elemental analysis,and their crystal structures were determined by X-ray single crystal diffraction.The cluster 2a-2i contains two pyridine methanol ligands,which coordinate with two Ru atoms.Two pyridine N atoms coordinate directly with two Ru atoms through coordination bonds.The O atoms of pyridine alcohol coordinate with two Ru atoms simultaneously in the form of?₂-O bridge,forming a stable N,O five-membered ring structure.The ruthenium clusters 3a,3j,3k and 3l are similar in coordination to 2a-2i,but have only one pyridine methanol ligand.2.Ruthenium clusters 2a-2i were used as catalysts and t-BuOOH as oxidant for alcohol oxidation reaction.Ruthenium clusters 2a-2i all showed good catalytic activity in alcohol oxidation reaction,and ruthenium cluster 2d had the best catalytic activity.Meanwhile,the catalytic system has a good catalytic effect on aromatic primary alcohols and secondary alcohols.The aromatic primary alcohols and secondary alcohols were respectively oxidized to the corresponding aldehydes and ketone compounds,and the yields were up to 90%.3.Ruthenium complexes 2a-2i were used as catalyst,t-BuOK was used as co-catalyst,and ambient air was oxygen source for the oxidation of amine to amide.The catalytic yields were 74%-93%.The ruthenium clusters 2a-2i exhibited good catalytic effects in the oxidation of amines to amides,and the catalytic effects of 2a,2c and 2d were excellent.