Synthesis And Characterization Of Complexes Of Multi-phosphines With Transition Metals

Organic phosphines have attracted much attention due to their versatile coordination modes and the rich applications in catalysis, medicine and optical materials. Multi-phosphines can easily react with metals to form various interesting structures because they have several donor atoms and flexible coordination modes. Studies on the complexes of these ligands are mainly involved in the formation of metal cage-like or metallocyclic complexes containing novel frameworks with Ag(â… ), Pt(â…¡) etc., the stabilization of metal complexes containing low oxidation state, catalyzing organic reactions by binding at Rh or Ir, and the formation of new luminescent materials while coordinated with Au(â… ).In this thesis, we selected a tetra-phosphine N, N', N'-tetra(diphenylphosphanylmethyl)ethylene diamine (dppeda) (1) and its oxidized form (dppedaO₄) as the starting reagents, which react with Ag(â… ),Co(â…¡) and Ni(â…¡) to form five new complexes. All compounds were characterized by elemental analyses, IR spectra, ¹H(³¹P) NMR, and X-ray single-crystal diffraction. The solid-state photoluminescent properties of two of the five complexes were also investigated. The contents of this thesis are described as follows:1) The syntheses, structures, and applications of multi-phosphines are reviewed.2) The reaction of dppeda (1) with AgNO₃ and AgCl afforded a binuclear complex [Ag₂(dppeda)Cl](NO₃)·2MeOH (2) while the analogous reactions using AgSCN and dppeda gave rise to a polymeric complex [Ag₂(dppeda)(SCN)₂]_n (3). Treatment of 1 with AgNO₃ and thiosemicarbazi(o)ne produced an unexpected complex [Ag₂{(Ph₂PCH₂)₂NNHCSNH₂}₂](NO₃)₂·2CH₃OH (4·2CH₃OH). The cation of 2 shows an interesting molecular basket framework in which dppeda adopts a side-by-side coordination mode, while 3 possesses a unique 2D (6, 3) layer network with a 34-membered macrocycles in which dppeda adopts an end-to-end coordination mode, Such a topological framework of 3 is unprecedented in the chemistry of tetraphosphines. Like those of less complicated diphospine ligands, dppeda in 2 or 3 works as a doubly-bridging ligand. Both 2 and 3 in solid state emits fluorescence at room temperature when they are irradiated by UV light. Upon excitation at 310 nm (2) and 342 nm (3), they exhibit photoluminescence with emission maxima at ca. 390 nm and 413 nm. In the dications of 4, two PPh₂CH₂(?) groups in dppeda cmbine with =NNHCSNH₂,yielding a new bi-phosphine ligand (Ph₂PCH₂)₂NNHCSNH₂.Two Agions interact with two (Ph₂PCH₂)₂NNHCSNH₂ ligands to form a saddle-like structure.3) The oxidation of dppeda by H₂O₂ afforded an oxidized ligand dppedaO₄ (5).The reactions of 5 with CoCl₂·6H₂O gave rise to a binuclear complex Co₂(dppedaO₄)Cl₄ (6). By addition of (C₂H₅)₂NCS₂^-(dtc) into the mixture of dppeda and NiCl₂,a stable binuclear compound [Ni₂(dppeda)₂(dtc)₂](PF6)₂·1.5CH₂Cl₂ (7·1.5CH₂Cl₂) was formed. The two Co atoms in 6 adopt octahedral and tetrahedral geometries, respectively. DppedaO₄ adopts aμ₂-η¹-η⁵ coordination mode, in which both O and N atoms are involved in the coordination at Co centers. In the cations of 7, each of the Ni atoms binds to two P from dppeda and two S atoms from dtc to form asquare planar coordination geometry while dppeda holds an end-to-end coordination mode.