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