Synthesis And Catalytic Applications Of Transition Metal Complexes Of Functionalized N-Heterocyclic Carbenes

Due to their excellent σ-donor properties, ease of synthesis, and variable steric bulk, N-heterocylic carbenes (NHCs) have gained increasing attention in recent years. Their transition metal complexes have been widely used in olefin metathesis, hydrogenation, and cross coupling reactions. Hence, the design and synthesis of transition metal complexes is of importance in organometallic chemistry. This dissertation mainly includes four parts:(1) A family of ruthenium(Ⅱ) complexes have been prepared and fully characterized. Carbene transfer reactions of [Ru(p-cymene)Cl2]2,[Ru(CO)2Cl2]n and RuHCl(CO)(PPh3)3with silver-NHC complexes in situ generated afforded [RuL(CH3CN)2](PF6)2(2.1),[Ru2L(p-cymene)2Cl2](PF6)2(2.2),[RuL(CO)2](PF6)2(2.3), and [RuL(PPh3)2](PF6)2(2.4), respectively. Treatment of2.1with phen resulted in [RuL(phen)(CH3CN)](PF6)2(2.5). Reaction of dppe and2.1gave [RuL(dppe)(CH3CN)2](PF6)2(2.7), in which two pyridines were substituted by a dppe ligand. In contrast, reactions of2.1with ethane-1,2-diamine, propane-1,3-diamine, and3,5-dimethyl-1H-pyrazole led to substitution of CH3CN and subsequent N-H addition of the C=N bond of the coordinated CH3CN yielding [RuL(ethane-1,2-diamine)(N-(2-aminoethyl)acetimidamide)](PF6)2(2.8) and [RuL(propane-1,3-diamine)(N-(3-aminopropyl)acetimidamide)](PF6)2(2.9), and RuL(1-(3,5-dimethy1-1H-pyrazol-1-yl)ethanimine)(CH3CN)](PF6)2(2.10), respectively.(2) Pyridazine-based transition complexes of [Ru2Cl(L)(CH3CN)4](PF6)3(3.1),[Cu3La3](PF6)3(3.2),[Pd2(allyl)2L](PF6)2(3.3),[Pd2(allyl)2Lb2](PF6)2(3.4),and [NiLc2](PF6)2(3.5) have been synthesized and fully characterized.In complex3.1, ligand L binds to two Ru(Ⅱ) centers forming a well-behaved Ru2(L)Cl plane with a five-membered metallocyclic ring. Complex3.2is trinuclear containing a triangular Cu3unit bonded together by three La where one imidazolylidene was oxidized into imidazolone.Deprotonation reaction with Ag2O in CH3CN and CH3OH resulted in C-N cleavage of the imidazolium salt and subsequent reaction with [Pd(allyl)Cl]2 and Ni(PPh3)2Cl2gave3.4and3.5, respectively. Dinuclear Ru(II)-NHC complex3.1exhibits excellent catalytic activity for the oxidation of alkenes into diketones.(3) A planar π-conjugated naphthyridine-nased NHC Ligand (L=2,4-dimethyl-8-phenyl-[1,2,4]triazolo[4,3-a][1,8]naphthyridin-9-ylidene) and its silver, copper, cobalt, and nickel complexes [Ag2(L)2(CH3CN)2](PF6)2(1),[CuL(CH3CN)2](PF6)(2),[CuL(phen)](PF6)(3),[CuL(dppe)](PF6)(4),[Co(L)2(CH3CN)2](PF6)2(5), and [Ni(L)3](PF6)2(6) have been synthesized and fully characterized by NMR, elemental analysis, and X-ray diffraction analysis.Copper complex2exhibits excellent catalytic activity in Cu(I)-catalyzed azide-alkyne cycloaddition reaction of2,2,6,6-tetramethylpiperidinyl-l-oxy-tethered alkynes in an air atmosphere at50℃(4) A novel in-situ generated Cu/NHC/TEMPO catalyzed aerobic oxidation of primary alcohols to aldehydes was studied.Various substituted benzyl, allyl, propargyl alcohols have been applied in this catalytic system with high yields, and even the alkyl alcohols could be successfully transformed with10mol%catalyst loadings. Due to the property of ease of modification of NHC ligand, the effect of the ligand to the reaction could be systemically studied. Additionally, copper powder that was very cheap, was employed as the precatalyst, showing the potential of industrial applications.