固氮酶是地球上生物固氮的关键，模拟固氮酶实现人工常温常压固氮一直是人们研究的热点，特别是确定了固氮酶的活性中心是富含硫的铁钼簇（FeMoco）之后，分子模型催化剂得到了更加充分地发展。本课题针对目前过渡金属（Fe, Mo）分子模型催化剂存在的催化条件苛刻、配体合成复杂、与固氮酶的结构不符、引入大量还原剂和质子酸、催化剂在短时间内分解失活等缺点和不足，打破常规强场配体的限制，拟合成一系列多硫CSSS型类固氮酶弱场配体辅助的过渡金属（Fe和Mo）配合物，在合适质子源和还原剂存在下，研究其固氮性能。探究不同配体的空间位阻及电子性质，质子源酸性，还原剂的还原能力影响氮气还原的规律；重点考察弱场配体存在下，金属中心的氧化态，自旋状态，磁学性质，及这些因素对氮气还原的影响；探索配位模式与氮气反应性的关系，期待设计的CSSS型配体辅助配位的Fe, Mo催化剂能够精确模拟FeMoco高效率室温合成氨。

Nitrogenase is the key to biological nitrogen fixation on the earth. It is a hot research topic to simulate nitrogenases to achieve artificial nitrogen fixation at room temperature and atmospheric pressure. Especially after the identification that the active site of nitrogenase is sulfur-rich Fe-Mo cluster (FeMoco) with an interstitial carbon atom at the center, molecular model catalysts have been more fully developed. This topic is aimed against the deficiency among the current transition metal (Fe, Mo) molecular model catalysts, involving that the catalytic conditions are harsh, the ligand synthesis is complex, is inconsistent with the structure of nitrogenase, the introduction of a large number of reducing agents and protic acid, the decomposition and deactivation of the catalyst in a short time, etc. To break the limitation of conventional strong field ligands, we want to prepare a family of transition metal (Fe and Mo) complexes supported by polysulfide CSSS type weak field ligand structurally similar to nitrogenase enzymes for the purpose of nitrogen fixation in the presence of suitable proton source and reducing agent. The steric hindrance and electronic properties of different ligands will be explored. The influence on nitrogen reduction about the proton source acidity and the reducing ability of the reducing agent will be investigated. The oxidation state, spin state and magnetic properties of the metal center with weak field ligands will be highlighted. The relationship between coordination mode and nitrogen reactivity will be explored. It is expected that the Fe, Mo catalyst can accurately simulate FeMoco to synthesize ammonia high-efficiency room temperature at atomic-economy manner.