Hydrazido Species Research Articles

Trapping of a Terminal Intermediate in the Boron-Mediated Dinitrogen Reduction: Mono-, Tri-, and Tetrafunctionalized Hydrazines in Two Steps from N2.

The addition of chlorotrimethylsilane to a boron-mediated, transition-metal-free N2 activation reaction leads to the isolation of multiple potassium boryl(silyl)hydrazido species, likely trapping products of a terminal dinitrogen complex of boron. One of these silylated N2 species can be protonated or methylated, providing access to mono- to tetrafunctionalized hydrazines in two steps from N2 and in the absence of transition metals.

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

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-NxHy 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.

Mononuclear Five- and Six-Coordinate Iron Hydrazido and Hydrazine Species

This article describes the synthesis and characterization of several low-spin iron(II) complexes that coordinate hydrazine (N(2)H(4)), hydrazido (N(2)H(3)(-)), and ammonia. The sterically encumbered tris(di-meta-terphenylphosphino)borate ligand, [PhBP(mter)(3)](-), is introduced to provide access to species that cannot be stabilized with the [PhBP(Ph)(3)](-) ligand ([PhBP(R)(3)](-) = PhB(CH(2)PR(2))(3)(-)). Treatment of [PhBP(mter)(3)]FeMe with hydrazine generates the unusual 5-coordinate hydrazido complex [PhBP(mter)(3)]Fe(η(2)-N(2)H(3)) (1), in which the hydrazido serves as an L(2)X-type ligand. Upon coordination of an L-type ligand, the hydrazido shifts to an LX-type ligand, generating [PhBP(mter)(3)]Fe(L)(η(2)-N(2)H(3)) (L = N(2)H(4) (2) or NH(3) (3)). In contrast, treatment of [PhBP(Ph)(3)]FeMe with hydrazine forms the adduct [PhBP(Ph)(3)]Fe(Me)(η(2)-N(2)H(4)) (5). Complex 5 is thermally unstable to methane loss, generating intermediate [PhBP(Ph)(3)]Fe(η(2)-N(2)H(3)), which undergoes bimolecular coupling to produce {[PhBP(Ph)(3)]Fe}(2)(μ-η(1):η(1)-N(2)H(4))(μ-η(2):η(2)-N(2)H(2)). The oxidation of these and related hydrazine and hydrazido species is also presented. For example, oxidation of 1 or 5 with Pb(OAc)(4) results in disproportionation of the N(2)H(x) ligand (x = 3, 4), and formation of [PhBP(R)(3)]Fe(NH(3))(OAc) (R = Ph (9) and mter (11)).