Catalytic Nitrogen-to-Ammonia Conversion by Osmium and Ruthenium Complexes.

ABSTRACT: 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 N₂-to-NH₃ conversion (N₂RR), nor have M-N_xH_y complexes been derived from protonation of their M-N₂ precursors. To help delineate factors for N₂RR catalysis, we report on isostructural tris(phosphino)silyl Ru and Os complexes that mediate catalytic N₂RR, and compare their activities with an isostructural Fe complex. The Os system is most active, and liberates more than 120 equiv NH₃ per Os center in a single batch experiment using Cp*₂Co and [H₂NPh₂][OTf] as reductant and acid source. Isostructural Ru and Fe complexes generate little NH₃ under the same conditions. Protonation of Os-N₂^- affords a structurally characterized Os=NNH₂⁺ hydrazido species that mediates NH₃ generation, suggesting it is a plausible intermediate of the catalysis. Inactive Os hydrides are characterized that form during catalysis.

SUBMITTER: Fajardo J 

PROVIDER: S-EPMC6019285 | biostudies-literature | 2017 Nov

REPOSITORIES: biostudies-literature