碗状铀（III）有机络合物的合成及其对CO2活化转化的研究

The activation and transformation of carbon dioxide has attracted much attention in the last few decades as a contributor to the greenhouse effect and climate change. The bowl-shape trivalent uranium coordination complexes [LU] (L= (RArO)3tacn) stabilized by macrocyclic chelating ligands have shown good property in CO2 activation and functionalization, but the utility and practicality of uranium as a catalyst is questioned due to the problems such as uncontrollable reactivity and the regeneration of trivalent uranium. In this project, bowl-shape trivalent uranium coordination complexes [LU] (L= (RArO)3tacn) with proper reactivity will be synthesized via controlling the steric hindrance by altering R groups. The synthesized trivalent uranium catalyst [LU] (L= (RArO)3tacn)could react with CO2 leading to charge separated radical species [((RArO)3tacn)U(η1-OCO•-)], the radical anionic ligand OCO•- could react with other reagents simultaneously. In order to realize the catalyst regeneration, the catalytic reaction between CO2 and unsaturated compound (such as alkene, alkyne or diene) is designed. In the catalytic reaction, the catalyst trivalent uranium could regenerate via single-electron transformation with the product cyclic carbonate formed simultaneously. This project will open the door for uranium (III) complex catalytic reactions between CO2 and small molecular organic compounds, laying the foundation for the peaceful use of depleted uranium.

因温室效应导致的全球变暖日益严重，CO2的活化转化备受关注。大环螯合配体稳定的碗状铀(III)络合物[LU](L=(RArO)3tacn)对CO2有较好的反应活性，但因反应活性难控，U(III)络合物循环再生困难等问题尚未实现催化反应。本项目拟通过[LU]中配体取代基R位阻大小调控碗状铀(III)络合物的反应活性，筛选出能与CO2发生单电子转移反应生成亚稳态的电荷分离自由基活性物种[((RArO)3tacn)U(IV)(η1-OCO•-)]的铀(III)络合物催化剂。同时，设计[LU]催化CO2与不饱和烃化合物（如烯烃、炔烃、共轭二烯及共轭烯炔）反应。该反应能通过分子内单电子转移还原U(IV)络合物，同时产物以环状碳酸酯脱离U(III)实现U(III)催化剂循环再生。本项目将填补铀(III)络合物催化CO2与小分子有机物反应的空白，为贫化铀的和平利用打下基础。

通过本项目，掌握了不同取代基配体(RArOH)3tacn及其前体2-取代-4-叔丁基苯酚RArOH（R=叔丁基、环己基、1-甲基-环己基、金刚烷及1-苯基-环己基）的制备和纯化方法。完成了不同取代基(RArOH)3tacn（R=叔丁基、环己基、1-甲基-环己基、金刚烷及1-苯基-环己基）配位的铀（IV）络合物[((RArO)3tacn)UX]的制备，检验了其对CO2没有反应活性。