Design, Syntheses And Catalytic Properties Of Complexes With Tetraphosphine Ligands

Multidentate phosphines are a group of interesting ligands for the assembly of transition metal/phosphine complexes due to their abundant electron donors, rich coordination modes and tunable molecular configurations. These complexes have been confirmed to exhibit promising applications in medicine, optical materials and catalysis. Therefore, the design and synthesis of metal multiphosphine complexes with different structures could not only enrich their structural chemistry, but also develop their potential applications in materials science.In this thesis, we selected two analogous tetraphosphine ligands N,N,N’,N’-tetra(diphenylphosphanylmethyl)ethylene diamine(dppeda) and N,N,N’,N’-tetra(diphenylphosphanylmethyl)-p-phenylene diamine(dpppda). The assembly reactions of both ligands with Ni Cl2 and Ag NO3 led to the formation of three complexes. Their structure determination and the spectra characterization were performed diligently. Their catalytic activities toward the ring-open polymerization(ROP) of ε-caprolactone(ε-CL) and the photodegradation of aromatic compounds were also investigated. This dissertation mainly focused on:(1) The metal complexes of various multiphosphine ligands along with their catalytic properties and applications are reviewed.(2) As an extension of the undergraduate thesis of my own, I continued repeating all the characterization data and catalytic data and finally summarized the results into a paper. The reactions of Ni Cl2 with dppeda or dpppda in the presence of an ancillary ligand Na S2CN(C2H5)2(Na(dtc)) afforded two dimeric complexes: [(dtc)Ni(dppeda)Ni(dtc)](PF6)2?5C6H14(1?5C6H14) and [(dtc)Ni(dpppda)Ni(dtc)](PF6)2?2CH3OH(2?2CH3OH). Compounds 1 and 2 were characterized by elemental analyses, IR spectra, 1H, 13C{1H} NMR and 31P{1H} NMR, electrospray ionization(ESI) mass spectra, thermogravimetric(TGA) experiments and single crystal X-ray diffraction. Both compounds have similar dinuclear cationic structures, in which one tetraphosphine ligand chelates two Ni(dtc) units. Both dppeda and dpppda adopt the end-to-end coordination mode in 1 and 2. We studied their catalytic performance in the ring-opening polymerization(ROP) of ε-caprolactone(ε-CL), while 1 exhibited a higher catalytic activity than 2. Influencing factors such as solvents, temperatures, the ratios of ε-CL to catalyst, the presence of benzyl alcohol, concentrations of ε-CL and reaction intervals were investigated. The proposed ring-opening polymerization mechanism was studied by end-group analysis of the oligomer of ε-CL.(3) Reaction of Ag NO3 with dpppda gave rise to a coordination polymer [Ag4(NO3)4(dpppda)]n(3). Compound 3 was characterized by elemental analyses, IR spectra, 1H and 31P{1H} NMR, powder X-ray diffraction and single crystal X-ray diffraction. Each dpppda adopts a Z-shaped ?-?????? side-by-side mode via four Ag-P bonds. Each [Ag4(NO3)4] fragment in 3 connects its two equivalent ones via dpppda to form a 1D chain extending along the a axis. The band gap energy(Eg) of 3 possesses the nature of semiconductivity. Compound 3 exhibited good catalytic activity in the degradation of three nitroaromatics(nitrobenzene(NB), paranitrophenol(PNP) and 2,4-dinitrophenol(2,4-DNP)) and azo compounds under UV irradiation. In addition, 3 was quite stable during the catalysis. The photodegradation reactions adopted a pseudo-zero-order kinetics, and were supposed to take a ?OH radical-mediated mechanism. The complete decomposition of these compounds in water was accompanied by the almost quantitative evolution of CO2.