Double hydrogen atom abstraction from (TMP)Os(NH) (TMP = tetramesitylporphyrin) with phenoxyl or nitroxyl radicals leads to (TMP)Os(NH). This unusual bis(amide) complex is diamagnetic and displays an N-H resonance at 12.0 ppm in its H NMR spectrum. H-N correlation experiments identified a N NMR spectroscopic resonance signal at -267 ppm. Experimental reactivity studies and density functional theory calculations support relatively weak N-H bonds of 73.3 kcal/mol for (TMP)Os(NH) and 74.2 kcal/mol for (TMP)Os(NH)(NH). Cyclic voltammetry experiments provide an estimate of the p of [(TMP)Os(NH)]. In the presence of Barton's base, a current enhancement is observed at the Os(III/II) couple, consistent with an ECE event. Spectroscopic experiments confirmed (TMP)Os(NH) as the product of bulk electrolysis. Double hydrogen atom abstraction is influenced by π donation from the amides of (TMP)Os(NH) into the d orbitals of the Os center, favoring the formation of (TMP)Os(NH) over N-N coupling. This π donation leads to a Jahn-Teller distortion that splits the energy levels of the d and d orbitals of Os, results in a low-spin electron configuration, and leads to minimal aminyl character on the N atoms, rendering (TMP)Os(NH) unreactive toward amide-amide coupling.
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