Synthesis Of Copper And Iron Complexes And Their Directly Catalytic Oxidation Of Benzene Into Phenol By H₂O₂

Inspired by the cluster skeleton of dinuclear copper and iron centers in methanemonooxygenase, this thesis reported the design and synthesis of multi-dentatechelating ligands containing {N,O} atoms and their coordination chemistry to copperor iron ions. Further research in development of the copper or iron complexes ashomogeneous catalyst on their direct catalytic oxidation of benzene by hydrogenperoxide for preparation of phenol was carried out. The main research contentsincluded: the structure-activity relationship between the composition of chelatingligands and the controllability and stability in synthesis of clusters will beinvestigated; The influences of complexe skeleton topology, metal core numbers,metal coordinated structure, metal coordination unsaturation, and complexes stabilityon the catalytic activity and selectivity were addressed. At the same time, the effectsof substrate, oxidant, catalyst, solvent systems, raction temperature and time on thecatalytic properties were investigated. The main results were briefly summaried as thefollowing three parts:1. Reacting a heptadentate ligand,2,2’-(((pyridine-2,6-diylbis(methylene))bis-((pyridin-2-ylmethyl)-azanediyl))bis(methylene))diphenol (H2L), with one equivalentof CuCl2·6H2O, NiCl2·6H2O and FeCl3·6H2O, followed by anions exchange with PF6,BPh4and ClO4formed three mononuclear complexes [Cu(H2L)](Cl)(PF6)(1),[Ni(HL)](BPh4)(2) and [Fe(L)](ClO4)(3), respectively. Their structures in solid statewere determined by X–ray crystallography. In addition, the electrochemistry and theircatalytic activity in the oxidation reaction of benzene to phenol by H2O2wereinvestigated.2. Reaction of a heptadentate ligand (H2L) and a hexadentate ligand (H2LП)with three equivalents of Cu(ClO4)2·6H2O in methanol under basic condition affordeda hexanuclear cluster [Cu6(L)2(OH)4](ClO4)4·2DMF·3Et2O (4) and a nonanuclearcluster [(Cu9(LП)3(OH)7)](ClO4)5·0.25CH3OH·1.15H2O (5), respectively, whereH2LП2,2’-((((5-methyl-1,3-phenylene)bis(methylene))bis((pyridin-2-ylmethyl)azane -diyl))-is(methylene))bis(4-methylphenol). The structures of both clusters in theirsolid states have been determined by X-ray crystallography. NMR spectroscopicanalysis, conductivity measurements and ESI-MS analysis suggest that the clustersretain their structural integrities in solution. Both clusters show catalytic activitytowards the hydroxylation of benzene into phenol with hydrogen peroxide (H2O2) asan oxidant at80℃in aqueous acetonitrile. The conversion rate is about20%andtheir TON/TOF are558/186and896/299for clusters4and5, respectively.3. Two multidentate ligands2,2’-(1,1’-(pyridine-2,6-diylbis(methylene))bis(1H-1,2,3-triazole-4,1-diyl))bis(methylene)bis((pyridin-2-ylmethyl)azanediyl)bis(methylene)diphenol (H2LI) and N,N’-((1,1’-(pyridine-2,6-diylbis(methylene))bis(1H-1,2,3-triazole-4,1-diyl))bis(methylene))bis(1-(pyridin-2-yl)-N-(pyridin-2-ylmethyl)methanamine)(LΠ) containing triazolyl, phenolate and pyridinyl groups were prepared byclick reaction between diazide and terminal alkynes in the presence of catalyst CuI.Both ligands were reacted with Cu2+and Fe3+salts to give three dinuclear complexes[LICu2](BPh4)2·2DMF (6),[LΠ(DMF)2Cu2](ClO4)4·H2O (7) and [LΠ(FeCl2)2](PF6)2(8). All complexes were characterized by IR, element analysis and UV–Vis spectra. Inaddition, the electrochemistry and their catalytic activity in the oxidation reaction ofbenzene to phenol by H2O2were investigated. Because of metal bond, catalyticactivity of complex6is higher than that of complexes7,8.Through this research we will hope to obtain effective copper or iron clustercatalysts with potential application in industrial field, clarify the catalystic mechanism,summarize the relationship between structure and activity in oxidation of benzene tophenol catalyzed by copper or iron clusters. This research was very important to thedevelopment of the relative environmental and green process for directly oxidationbenzene into phenol, as well as to have theoretical significance to give deep insightinto the catalytic reaction mechanism with the multinuclear metal cluster compoundsby catalytic oxidation of benzene to phenol.