Synthesis and Characterization of Novel N-heteocyclic Carbene and Indenylidene Ligands
|Course||Polymer Chemistry and Physics|
|Keywords||Olefin metathesis ruthenium-based catalyst N-heterocyclic carbeneligands indenylidene ligands|
Olefin metathesis is a kind of reaction with carbon frame rearrangementbetween double or triple bond with ending group exchange at the same time, whichis widely used in chemical, pharmaceutical and polymer materials industry; take animportant part in the development of the society, human life. In development of thisprocess, the presence of catalyst plays a significant role; it implements the couplingwhich is inert in common sense among double or triple bonds; greatly expand theimaginary space for people in the construction of compounds skeleton, thusdeveloping new efficient catalysts has increasingly attracted people’s attention,which the novel ruthenium-based catalyst synthesis has become a hotspot in the fieldof chemistry. But there are still many problems in this field, such as the synthesis oftetra-substituted and electron-deficient olefins, olefin metathesis in polar solvent andhow to improve the stability of the catalysts. This paper would like to design andsynthesize novel ruthenium-based olefin metathesis catalysts with potentialapplications from modification of N-heterocyclic carben ligands and indenylideneligands.Firstly, the aniline and oxalyl chloride were used as raw material,N-heterocyclic carbene ligands:[N,N’-bis（2,4,6-trimethylphenyl）imidazolin-ium·NO3-/HSO4-and N,N’-bis（2,6-diisopropylphenyl）imidazolinium·NO3-/HSO4-]were successfully synthesized through a series of reactions; the nitro-group wasintroduced to these ligands, and then two new ligands N,N’-bis（2,4,6-trimethyl-3,5-dinitrophenyl）imidazolium·NO3-/HSO4-and N,N’-bis（2,6-diisopropylphenyl-3/5-nitrophenyl）imida-zolium·NO3-/HSO4-were obtained. Their structures werecharacterized by1H NMR,13C NMR and MS and the latter ligand has not beenreported. We tried to synthesize novel ruthenium complexes with these two ligandsbut failed due to the high steric hindrance of ligands.Secondly, two new indenylidene ligands with electron-withdrawing groupswere obtained through introducing-Cl or-Br group by two differeny way. Theirstructures were characterized by1H NMR and13C NMR. The two new indenylidene ligands were also used to prepare their corresponding ruthenium complexes, but akind of dimmer ruthenium complexes was given instead of the target compounds,which were demonstrated by31P NMR spectrum. In conclusion, probably the twokinds of indenylidenes with electron-withdrawing groups impede the process insteadof promoting the formation of catalyst. Anyway, this result would provide some ideafor the mechanism of indenylidene catalyst formation and designation of newindenylidene ruthenium-based catalysts.