Syntheses, Structures And Catalytic Properties Of Metal Complexes Of2,6-Di(1H-pyrazol-3-yl)pyridine

The coordnation compounds of N-containing tridentate ligands have receivedmuch attention because of their special applications in the fields of advanced materials,molecular recognition, ion exchange, catalysis and self-assembly of supramolecularcompounds. The ligand2,6-di（1H-pyrazol-3-yl）pyridine （bppyH2） was chosen in thisdissertation to prepare a series of mononuclear or dimeric complexes. These complexeswere characterized by elemental analysis, IR spectra, luminescent spectra andsingle-crystal X-ray diffraction analysis. The main contents of this thesis are describedas follows:Reaction of BppyH2with Cu（II）, Cd（II）, or Fe（III） salts afforded seven newcoordination compounds [Cu₂（bppyH₂）2（ClO₄）₂]（1），[Cu)₂（bppyH）₂（ClO₄）₂]·DMF（1·2DMF），{[Cu（bppyH₂）（μ-ClO₄）]（ClO₄）·（MeCN）}_n（2），[Cd（bppyH₂）（NO₃）₂]（3），[Cd（bppyH2）（dca）2]（4），[Cd（bppyH₂）Cl₂]（5），[Fe（bppyH₂）Cl₂]（6） and[Fe（bppyH2）₂]（NO₃）₂·2MeOH （7）[bppyH₂=2,6-di（1H-pyrazol-3-yl）pyridine],respectively. Compounds1⁷were characterized by elemental analysis, IR spectroscopy,and single-crystal X-ray Diffraction. Compounds3,4,5,6and7are mononuclearcompounds while1and1·2DMF are dimeric compounds in which each centralcopper（II） has a tetragonal pyramid coordination geometry. Compound2has a1D linearchain （extending along the b-axis） in which each [Cu（bppyH2）（MeCN）]+fragment linksits equivalent ones via bridging perchlorate anions. Compound5shows a1D chainwhich links its equivalent ones through intermolecular hydrogen-bonding interactionsbetween the H atom of N-pyrazole and Cl atom and the π···π interactions betweenN-pyrazolyl and pyridyl groups.The solvothermal reactions of bppyH₂with CuCl₂·2H₂O gave a knownmononuclear complex [CuCl₂（bppyH₂）]（8, bppyH₂=2,6-di（1H-pyrazol-3-yl）pyridine）.Treatment of8with2equiv. of AgNO3in DMF gave rise to a binuclear Cu（II） complex [Cu2（bppyH）₂（NO₃）₂]（bppyH=2-（pyrazol-3-yl）-6-（pyrazolate）pyridine）（9·2DMF）.Complex9·2DMF was characterized by elemental analysis, IR and single crystal X-raydiffraction. Complex9·2DMF has a dimeric structure in which the two Cu（II） centersare bridged by a couple of the situ-generated bppyH-anions. Each Cu（II） center isfurther coordinated by one O atom of a NO3-anion and three N atoms of one bppyH-anion, which formed the tetrahedron structure. Under the mild polymerizationconditions, compounds9·2DMF and8exhibited a higher catalytic activity in thepolymerization of methyl methacrylate （MMA）. Solvents, reaction temperatures, andthe ratios of MMA to catalyst had significant effects on the polymerization of MMA. InCy-one, complex9·2DMF showed the high activity at80oC. Almost completeconversion of the monomer into PMMA （MMA/2=300/1） was achieved within4h at80oC in Cy-one with a narrow polydispersity index （PDI=1.22）. Complex9·2DMFexhibited a higher catalytic activity in the polymerization of methyl methacrylate（MMA） than the precursor complex8. The latter9·2DMF got much narrower PDI thanthe former8. In addition, we studied the possible mechanism for the MMApolymerization initiated by8and9·2DMF.