基于金属卡宾的氮气活化与转化的均相催化反应的理论计算研究

Activation and conversion of dinitrogen (nitrogen fixation) under mild conditions is of great importance for the sustainable development of human society. Nitrogen-containing organic compounds are widely used in the areas of organic chemistry, medicinal chemistry, and material chemistry. Thus, the direct transformation of abundant dinitrogen into N-containing organic compounds has huge application potential. However, reports on the synthesis of N-containing organic compounds directly using dinitrogen as nitrogen source are very rare, and the corresponding homogeneous catalytic cycle has not been achieved yet. In this project, we will carry out systematic theoretical studies on homogeneous catalytic nitrogen fixation by using quantum chemical methods. We will explore a new type of nitrogen activation mode based on metal-carbene species. We will investigate the mechanism of nitrogen activation by metal-carbene, and understand the characteristics of how the variations of functional groups on the metal-carbene precursors affect the thermodynamics of the nitrogen fixation process, and obtain the structure-relationship between the catalyst structure and the catalytic activity. On the basis of mechanistic understandings, we will then screen and design the substrates and catalysts to computationally achieve the homogeneous catalytic cycle for converting dinitrogen into N-containing compounds with good thermodynamics and kinetics that are potentially accessible under mild experimental conditions. The research results of this project will be helpful for developing new types of nitrogen activation mode and providing new thoughts for designing of catalytic cycles for nitrogen fixation. The newly designed catalytic cycles could be used as reference models for experimental exploring when developing new catalytic reaction systems for the transformation of dinitrogen into N-containing compounds.

实现温和条件下的氮气活化与转化（固氮）对于人类社会的可持续发展具有非常重要的意义。含氮有机物广泛应用于有机合成化学、药物化学和材料化学等领域，因此，直接以丰富易得的氮气为氮源合成含氮有机物具有巨大的潜在应用价值。然而，直接利用氮气合成含氮有机物的研究却很少，其均相催化循环还未实现。本项目拟采用量子化学计算方法，开展均相催化固氮反应的理论计算研究：探索一种新的基于金属卡宾的氮气活化模式；阐明金属卡宾活化氮气的化学本质；掌握反应底物上官能团的变化对反应热力学的影响规律；建立催化剂的结构和催化活性的构效关系；在机理研究的基础上，筛选并优化设计出合适的反应底物和高活性的催化剂，从理论上构建热力学和动力学可行的以氮气合成含氮有机物的均相催化循环。本项目的研究结果将对现有的氮气活化模式提供有效补充，为催化固氮循环的设计提供新的思路，为实验上发展以氮气合成含氮有机物的均相催化体系提供理论参考模型。

含氮有机物广泛应用于有机合成化学、药物化学和材料化学等领域，实现以氮气原料合成含氮有机物具有非常重要的意义。在本项目中，我们利用理论计算的方法，在机理研究的基础上，理性设计温和条件下的催化固氮循环。我们从理论上构建了基于金属卡宾的催化固氮循环。然后我们针对目标反应的热力学、动力学以及活性催化中心的特点进行了系统的理论研究，研究结果表明：i) 吸电子基团能有效稳定中间产物；ii) 前过渡金属生成的卡宾太稳定而不太适宜作为固氮反应的催化剂；iii) 共轭炔酮、共轭炔硫酮、共轭炔亚胺化合物、乙酸炔丙酯以及环丙烯等化合物作为卡宾前驱体的固氮反应的热力学不太理性；iv) 硼宾活化氮气和活泼醛类化合物作为卡宾前驱体固氮反应的策略具有较大潜力。该项目的研究结果将为进一步发展和完善以氮气合成含氮有机物的催化体系提供理论参考。