Organocerium(IV) Chemistry

在稀土元素中，铈值得特别关注，因为它具有+2、+3和关键的+4氧化态。由于其高氧化电位，Ce（IV）化合物被常规应用于有机合成、生物无机化学、材料科学和工业催化（三元催化转化器、储氧等）。本研究项目的主要目标是合成和全面表征新型四价铈配位化合物和有机金属化合物。在稀土金属化学中，苯基碘（III）二氯将被确立为一种创新的氧化剂。铈（IV）酰胺和（硅基）酰胺以及含环戊二烯基和环四烯基配体的新型有机铈（IV）配合物是相关的目标。在特殊情况下，将合成相应的铀（IV）酰胺酸盐，以便首次对一系列类似的铈（IV）和铀（IV）配合物的结构和反应性进行比较研究。金属氯化物前体与非还原性烷基化剂（如ZnMe2或SnMe4）的反应可能会获得第一个具有sigma键烷基配体的有机铈（IV）配合物。此外，铈（III）烷基衍生物的直接氧化将被系统地研究作为一种替代的合成方案。为了防止可能的配体氧化，将使用特定的（辅助）配体组合。可以预见，局部的适度成功已经可能对有机铈（IV）化学的发展产生重大影响。该研究项目还针对Ce(III)/Ce（IV）氧化还原对的表面有机金属化学进行了研究。利用周期性介孔二氧化硅作为载体材料以及多相化的硅酰胺路线将是研究此类分子Ce（IV）表面物质稳定性和反应性的重要标准。

Among the rare-earth elements cerium deserves special attention since it has access to the oxidation states +2, +3, and crucially +4. Because of their high oxidation potential, Ce(IV) compounds are routinely applied in organic synthesis, bioinorganic chemistry, materials science, and industrial catalysis (three-way catalytic converters, oxygen storage, etc.). Primary goal of this research project comprises the synthesis and full characterization of novel coordination compounds and organometallics of tetravalent cerium. Phenyliodine(III) dichloride is to be established as an innovative oxidant in rare-earth metal chemistry. Cerium(IV) amidinates and (silyl)amides as well as novel organocerium(IV) complexes bearing cyclopentadienyl and cyclooctatetraenyl ligands are relevant targets. In particular cases, the corresponding uranium(IV) amidinates will be synthesized to allow for the first time for a comparative study of a series of analogous cerium(IV) and uranium(IV) complexes with respect to their structure and reactivity. The reaction of metal chloride precursors with non-reducing alkylating agents such as ZnMe2 or SnMe4 might give access to the first organocerium(IV) complexes featuring sigma-bonded alkyl ligands. Furthermore, direct oxidation of cerium(III) alkyl derivatives will be systematically investigated as an alternative synthesis protocol. In order to prevent possible ligand oxidation, particular (ancillary) ligand sets will be employed. It can be foreseen that a moderate topical success already could have major implications for the development of organocerium(IV) chemistry. The research project also aims at the surface organometallic chemistry of the Ce(III)/Ce(IV) redox couple. The utilization of periodic mesoporous silicas as support material as well as the heterogenized silylamide route will be crucial criteria for studying the stability and reactivity of such molecular Ce(IV) surface species.