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Published March 25, 2012 | public
Journal Article

Ru(I) metalloradical that catalyzes nitrene coupling to azoarenes from arylazides

Abstract

Our group recently studied the interaction between aryl azides and the Fe(I) complex, [SiP^(iPr)_3]Fe(N_2) ([SiP^(iPr)_3] = ([SiP^(iPr)_3] = (2-iPr_2PC_6H_4)_3Si-). This reaction was found to initially form an Fe(I) azide adduct, [SiP^(iPr)_3]Fe(N_3Ar), which subsequently exhibited clean unimol. decay. Interestingly, the major product of this decay was shown to be azoarene and the starting complex [SiP^(iPr)_3]Fe(N_2), and use of excess aryl azide demonstrated catalytic azoarene formation from [SiP^(iPr)_3]Fe(N_2). While several related stoichiometric reactions had been known, this example was noteworthy in that it represented a rare example of catalytic N-N coupling to yield azoarene from org. azides. Mechanistic studies suggested the formation of a transient Fe(III) imide complex, [SiP^(iPr)_3]Fe(NAr), following decay of [SiP^(iPr)_3]Fe(N_3Ar), which subsequently underwent 4e- reductive N-N coupling to produce azoarene. [SiP^(iPr)_3]Fe(NAr) is a reactive S = 1/2 species that was only observable by EPR spectroscopy in a frozen glass. In this regard, the recent isolation of the Ru(I) metalloradical, [SiP^(iPr)_3] Ru(N_2), and its interaction with p-CF_3C_6H_4N_3to yield the formally Ru(III) imide complex, [SiP^(iPr)_3]Ru(NC_6H_4CF_3), is noteworthy. [SiP^(iPr)_3]Ru(NC_6H_4CF_3) did not yield azoarene upon decay, and was stable enough for thorough characterization. We thus envisioned that use of other substituted aryl azides might yield similar metal imide species that would retain some stability for characterization, yet also exhibit N-N coupling reactivity as obsd. in the Fe system. In this talk I will report on recent results of our studies on [SiP^(iPr)_3]Ru(N_2) with substituted aryl azides. The tendency of the aryl azide to degrade in the presence of [SiP^(iPr)_3]Ru(N_2) to azoarene product, either stoichiometrically or catalytically, is dependent on the aryl-ring substitution pattern.

Additional Information

© 2012 American Chemical Society.

Additional details

Created:
August 19, 2023
Modified:
October 26, 2023