Whereas molybdenum dinitrogen complexes have played a major role as catalytic model systems of nitrogenase, corresponding tungsten complexes were in most cases found to be catalytically inactive. Herein, we present a modified pentadentate tetrapodal (pentaPod) phosphine ligand in which two dimethylphosphine groups of the pentaPodMe (P5Me) ligand have been replaced with phospholanes (Pln). The derived molybdenum complex [Mo(N2)P5Pln] generates 22 and the analogous tungsten complex [W(N2)P5Pln] 7 equivalents of NH3 from N2 in the presence of 180 equiv.s of SmI2(thf)2/H2O, rendering the latter the first tungsten complex chemocatalytically converting N2 to NH3. In contrast, the tungsten complex [W(N2)P5Me] generates ammonia from N2 only in a slightly overstoichiometric fashion. The reasons for these reactivity differences are investigated with the help of spectroscopic and electrochemical methods.

中文翻译：

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钨配合物介导的二氮向氨的化学催化转化


虽然钼二氮配合物作为固氮酶的催化模型系统发挥了重要作用，但在大多数情况下发现相应的钨配合物具有催化失活。在此，我们提出了一种改良的五齿四足 （pentaPod） 膦配体，其中 pentaPodMe （P5Me） 配体的两个二甲基膦基已被磷烷 （Pln） 取代。衍生的钼络合物 [Mo（N2）P5Pln] 在 180 当量 SmI2（thf）2/H2O 存在下从 N2 生成 22 和类似的钨络合物 [W（N2）P5Pln] 7 当量的 NH3，使后者成为第一种将 N2 化学催化转化为 NH3 的钨络合物3。相比之下，钨络合物 [W（N2）P5Me] 仅以略微过化学计量的方式从 N2 产生氨。这些反应性差异的原因在光谱和电化学方法的帮助下进行了研究。