N-Oxide Coordination to Mn(III) Chloride

We report on the synthesis and characterization of Mn(III) chloride (Mn^IIICl₃) complexes coordinated with N-oxide ylide ligands, namely trimethyl-N-oxide (Me₃NO) and pyridine-N-oxide (PyNO). The compounds are reactive and, while isolable in the solid-state at room temperature, readily decompose into Mn(II). For example, “[Mn^IIICl₃(ONMe₃)_n]” decomposes into the 2D polymeric network compound complex salt [Mn^II(µ-Cl)₃Mn^II(µ-ONMe₃)]_n[Mn^II(µ-Cl)₃]_n·(Me₃NO·HCl)_3n (4). The reaction of Mn^IIICl₃ with PyNO forms varied Mn(III) compounds with PyNO coordination and these react with hexamethylbenzene (HMB) to form the chlorinated organic product 1-cloromethyl-2,3,4,5,6-pentamethylbenzene (8). In contrast to N-oxide coordination to Mn(III), the reaction between [Mn^IIICl₃(OPPh₃)₂] and 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) resulted in electron transfer-forming d⁵ manganate of the [TEMPO] cation instead of TEMPO–Mn(III) adducts. The reactivity affected by N-oxide coordination is discussed through comparisons with other L–Mn^IIICl₃ complexes within the context of reduction potential.