【摘要】 进行了VCl₂（PPh₃）₂甲醇溶液光还原氮和放氢反应动力学的研究,提出了肼是氮还原为氨的中间物的动力学证据。说明Ⅴ（Ⅱ）络合物是活性物种。氮分子的光还原氢化反应的可能机理是:以形成线形桥式双核钒（Ⅱ）的双氮基络合物活化,受氢原子攻击,形成配位的二亚胺和游离的肼,肼再还原质子化变成氨。更多还原

【Abstract】 In the process of nitrogen fixation by nitrogenase or photosynthetic bacteria, the reduction of N2 is in competition with the reduction of H3O+ for electron. It was found that V(II) complex system behaved itself in some aspects like nitrogenase, but whether or not N2H4 is the intermediate of the reduction of N2 to NH3 and the active species is mononuclear or polynuclear are still in question. In this pamper, the kinetics of light induced N2 reduction and H2 evolution in VCl2(PPh3)2 methanol solution has been studied. Kinetic curve of the concentration of N2H4 and NH3 plotted against irradiation time exhibits a characteristic of consecutive reactions, and K2>>K1, showing that N2H4 is an intermediate of the reduction of N2 to NH3.The photoreaction temperature and the concentration of VCl2(PPh3)2 complex are advantageous to the reduction of N2H4 to NH3. The photoreduction of C2H2 in VCl2(PPhs)2 complex methanol solution was compared with the reduction of N2, C2H4 and C2H6 were detected, it was a spontaneous two-electronic reduction process. The change of electronic absorption spectra of VCl2(PPh3)2 in methanol under irradiation indicated that V(Ⅱ) was an active species which could be produced from V(Ⅲ) by photoreduction.According to the formation of hydrogen atom by light irradiation and only one electron transfer between V(Ⅱ) and V(Ⅲ), the possible mechanism of photoreduction of N2 to NH3 is that N2 is activated by means of forming dinuclear V(Ⅱ) complex, e. g. LnV(Ⅱ)...N... N ...V(Ⅱ)Lu, the two N atoms are attacked by hydrogen atom resulting in the formation of N2H2 and N2H4, then N2H4 is protonated to NH3.更多还原