The reactivity of MCl 3 (η 1 -TEMPO) (M = Fe, 1; Al, 2; TEMPO = 2,2,6,6-tetramethylpiperidine-N-oxyl) with a variety of alcohols, including 3,4-dimethoxybenzyl alcohol, 1phenyl-2-phenoxyethanol, and 1,2-diphenyl-2-methoxyethanol, was investigated using NMR spectroscopy and mass spectrometry. Complex 1 was effective in cleanly converting these substrates to the corresponding aldehyde or ketone. Complex 2 was also able to oxidize these substrates; however, in a few instances the products of overoxidation were also observed. Oxidation of activated alkanes, such as xanthene, by 1 or 2 suggests that the reactions proceed via an initial 1-electron concerted proton−electron transfer (CPET) event. Finally, reaction of TEMPO with FeBr 3 in Et 2 O results in the formation of a mixture of FeBr 3 (η 1 -TEMPOH) ( 23) and [FeBr 2 (η 1 -TEMPOH)] 2 (μ-O) (24), via oxidation of the solvent, Et 2 O.

Addition of TEMPO (TEMPO = 2,2,6,6‐tetramethylpiperidine‐N‐oxyl) to a toluene slurry of AlBr3 results in rapid formation of AlBr3(η1‐TEMPO) (1), which can be isolated in 65 % yield. In contrast, addition of TEMPO to a hexanes solution of BBr3 results in formation of [TEMPO][BBr4] (2) and (TEMPO)2BBr (3), the products of TEMPO disproportionation. Complexes 1–3 have been fully characterized, including analysis by X‐ray crystallography. The divergent reactivity is likely dictated by the Lewis acidity of the group 13 halide, and in the case of the stronger Lewis acid BBr3, coordination of TEMPO to the boron center generates an adduct that is capable of oxidizing free TEMPO.