Fajardo Javier, Peters Jonas C
Division of Chemistry and Chemical Engineering, California Institute of Technology , Pasadena, California 91125, United States.
J Am Chem Soc. 2017 Nov 15;139(45):16105-16108. doi: 10.1021/jacs.7b10204. Epub 2017 Nov 2.
Despite the critical role Ru and Os complexes have played in the development of transition metal dinitrogen chemistry, they have not been shown to mediate catalytic N-to-NH conversion (NRR), nor have M-NH complexes been derived from protonation of their M-N precursors. To help delineate factors for NRR catalysis, we report on isostructural tris(phosphino)silyl Ru and Os complexes that mediate catalytic NRR, and compare their activities with an isostructural Fe complex. The Os system is most active, and liberates more than 120 equiv NH per Os center in a single batch experiment using Cp*Co and [HNPh][OTf] as reductant and acid source. Isostructural Ru and Fe complexes generate little NH under the same conditions. Protonation of Os-N affords a structurally characterized Os=NNH hydrazido species that mediates NH generation, suggesting it is a plausible intermediate of the catalysis. Inactive Os hydrides are characterized that form during catalysis.
尽管钌和锇配合物在过渡金属二氮化学的发展中发挥了关键作用，但它们尚未被证明能介导催化氮到氨的转化（NRR），也没有从其M-N前体的质子化中得到M-NH配合物。为了帮助确定NRR催化的因素，我们报道了介导催化NRR的同结构三（膦基）硅基钌和锇配合物，并将它们的活性与同结构的铁配合物进行比较。锇体系活性最高，在使用Cp*Co和[HNPh][OTf]作为还原剂和酸源的单批次实验中，每个锇中心能释放超过120当量的氨。在相同条件下，同结构的钌和铁配合物产生的氨很少。锇-氮的质子化产生了一种结构特征明确的锇=NNH肼基物种，该物种介导氨的生成，表明它是催化过程中一个合理的中间体。对催化过程中形成的无活性锇氢化物进行了表征。
