| This thesis consists of two parts. In the first part, a series of new transition metal complexes with tetraaza ligands were synthesized. Partial transition metal(Cr, V) complexes were obtained with the central metals in high valence [Cr(III), V(IV)] from lower valent M(II)Cl2, and a possible reaction mechanism for this phenomenon was proposed. Catalytic properties of the IVB group metal complexes for ethylene polymerization were also studied. In the second part, an autocatalytic hydrogen evolution system of ammonia-borane was investigated and the reaction mechanism was preliminary examined. Detailed results are listed as follows:In chapter two, a series of transition metal complexes LAMCl2(M = V), LAMCl(M = V, Cr), LAM(M = Mn, Fe), LBMCl(M = Cr) and LBM(M = Mn, Fe) were synthesized from reactions of lithium salts of known tetraaza andilido-imine ligands, 1,2-[(2’-(2 ",6"-iPr2C6H3N=CH)C6H4NLi]2C6H4(LALi2) and 1R, 2R-[(2 ",6"-iPr2 C6H3NLi)-C6H4CH=N]2C6H10(LBLi2) with MCl2(M = V, Cr, Mn, Fe) and MCl3(M = V, Cr), respectively. All new complexes were characterized by elemental analysis, XPS and TGA, and partial complexes were determined by single crystal X-ray diffraction analysis. From the reaction of VCl2 with LALi2 and the reaction of Cr Cl2 and LBLi2, higher valent metal complexes LAV(IV)Cl2 and LBCr(III)Cl were obtained respectively. A possible reaction mechanism, in which a complex with a M(II) metal center forms first, followed by disproportionation reaction with MCl2 to give the high valent metal complex, was proposed.In chapter three, a series of IVB group metal complexes LAMCl2(M = Ti, Zr, Hf) were synthesized by one-pot HCl-elimination reaction of the free tetraaza andilido-imine ligand LAH2 with MCl4, and characterized by elemental analysis, 1H and 13 C NMR spectroscopy and single crystal X-ray diffraction analysis. Upon activation with AliBu3/Ph3C+B(C6F5)4- or MAO, these complexes exhibit moderate catalytic activity for ethylene polymerization, and produce polyethylene with ultra-high molecular weight(viscosity-averaged molecular weight Mη up to 4.29 × 106 Dalton).In chapter four, two new ligands 1,2-[(2’-(Ar NH)C6H4HC=N)]2C6H4 [Ar = 2,6-Me2C6H3(LC1H2), 2,6-iPr2C6H3(LC2H2)] were synthesized. A number of IVB group metal complexes bearing a partial deprotonated tridentate ligand LC1HMCl3(M = Ti, Zr, Hf) were obtained by one-pot HCl-elimination reaction of LC1H2 with MCl4. The complexes LC1MCl2 and LC2MCl2(M = Zr, Hf) with fully deprotonated tetradentate ligands were synthesized by the reaction of double lithium salt of the corresponding ligand with MCl4. All new complexes were characterized by elemental analysis, 1H and 13 C NMR spectroscopy, and the molecular structures of LC1Zr Cl2 and LC2Hf Cl2 were determined by single crystal X-ray diffraction analysis. Upon activation with Al R3/Ph3CB(C6F5)4 or MAO, these complexes exhibit moderate catalytic activity for ethylene polymerization and produce linear polyethylene with ultra-high molar masses(100 ~ 184 × 104 Dalton).In chapter six, an autocatalytic ammonia-borane hydrogen evolution system consisting of melamine/BH3 was investigated by following the reaction under different conditions. It was found that this system can release 5.7 wt% of hydrogen at 25 oC and 8.6 wt% of hydrogen at 195 oC with no need of any catalyst. The reaction product was characterized by IR, solid 11 B NMR, TGA and BET techniques. On the basis of these results, a possible reaction mechanism was proposed.In chapter seven, a similar ammonia-borane hydrogen evolution system with a model compound o-aminopyridine instead of melamine was investigated. A product with a definite structure was obtained and its structure was determined by X-ray diffraction analysis. This result further confirms the hydrogen evolution reaction mechanism proposed in chapter six. |
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