Isolable f-Element Diphosphene Complexes by Phosphinidene Group Transfer and Coupling at Uranium

The parent diphosphene (HPPH) molecule is of fundamental interest, but its reactive nature renders it challenging to isolate and study. Metal-stabilization is an attractive approach for studying HPPH, but molecular derivatives are limited to three complexes of p-/d-metals reflecting a scarcity of synthetic methods for rationally preparing HPPH complexes. Here, we introduce f-element HPPH complexes, adding to f-element diazenes (HNNH) that were first reported over thirty years ago. By utilizing 7<i>l</i>³-phosphadibenzonorbornadiene and uranium(III) reagents we show how parent diphosphene, phosphinidiide, and diphosphorus motifs can all be constructed, developing synthetic approaches for this area. Computed reaction profiles reveal common, initial reaction steps that subsequently diverge depending on the ancillary ligands, radical nature of intermediates, and the 7<i>l</i>³-phosphadibenzonorbornadiene P-substituent. Calculations demonstrate a surprising prevalence of open-shell radical intermediates, and that the redox chemistry is P-, not U-, centred. This work thus provides insights to inform future synthetic endeavours in this area.

母体二磷烯（HPPH）分子具有重要的基础研究价值，但其高反应活性使其难以分离并开展系统性研究。采用金属稳定化策略是研究HPPH的极具吸引力的途径，但目前该类分子衍生物仅局限于3种p区/d区金属配合物，这反映出可用于理性制备HPPH配合物的合成方法十分匮乏。本文首次报道了f区元素（f-element）HPPH配合物，丰富了三十余年前首次被报道的f区二氮烯（diazenes，HNNH）相关研究体系。通过利用7λ³-磷杂二苯并降冰片二烯与铀(III)试剂，我们成功构建出母体二磷烯、膦宾（phosphinidiide）及二磷骨架，并开发了该研究领域的合成方法学。计算得到的反应能垒曲线显示，反应存在共通的初始步骤，后续反应路径则会根据辅助配体、中间体的自由基特性以及7λ³-磷杂二苯并降冰片二烯的P位取代基发生分化。计算结果还揭示出开壳层自由基中间体的意外普遍性，且该体系的氧化还原化学过程以磷原子为中心，而非铀原子。本研究为该领域未来的合成研究提供了理论参考与新思路。