Tuning the Reactivity of TEMPO by Coordination to a Lewis Acid: Isolation and Reactivity of MCl3(η1-TEMPO) (M = Fe, Al)

Addition of 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO) to MCl3 (M = Fe, Al) results in the formation of MCl3(η1-TEMPO) [M = Fe (1), Al (2)]. Both 1 and 2 oxidize alcohols to generate ketones or aldehydes along with the reduced complexes MCl3(η1-TEMPOH) [M = Fe (3), Al (4)]. Complexes 1–4 were fully characterized, including analysis by X-ray crystallography. Additionally, control experiments indicated that neither MCl3 (M = Al, Fe) nor TEMPO are capable of effecting the oxidation of alcohols independently.