The addition of Sc(OTf) 3 and Al(OTf) 3 to the mononuclear Mn III -hydroxo complex [Mn III (OH)(dpaq)] + (1) gives rise to new intermediates with spectroscopic properties and chemical reactivity distinct from those of [Mn III (OH)(dpaq)] + . The electronic absorption spectra of [Mn III (OH)(dpaq)] + in the presence of Sc(OTf) 3 (1-Sc III ) and Al(OTf) 3 (1-Al III ) show modest perturbations in electronic transition energies, consistent with moderate changes in the Mn III geometry. A comparison of 1 H NMR data for 1 and 1-Sc III confirm this conclusion, as the 1 H NMR spectrum of 1-Sc III shows the same number of hyperfine-shifted peaks as the 1 H NMR spectrum of 1. These 1 H NMR spectra, and that of 1-Al III , share a similar chemical-shift pattern, providing firm evidence that these Lewis acids do not cause gross distortions to the structure of 1. Mn K-edge X-ray absorption data for 1-Sc III provide evidence of elongation of the axial Mn−OH and Mn−N(amide) bonds relative to those of 1. In contrast to these modest spectroscopic perturbations, 1-Sc III and 1-Al III show greatly enhanced reactivity toward hydrocarbons. While 1 is unreactive toward 9,10dihydroanthracene (DHA), 1-Sc III and 1-Al III react rapidly with DHA (k 2 = 0.16(1) and 0.25(2) M −1 s −1 at 50 °C, respectively). The 1-Sc III species is capable of attacking the much stronger C−H bond of ethylbenzene. The basis for these perturbations to the spectroscopic properties and reactivity of 1 in the presence of these Lewis acids was elucidated by comparing properties of 1-Sc III and 1-Al III with the recently reported Mn III −aqua complex [Mn III (OH 2 )(dpaq)] 2+ (J. Am. Chem. Soc. 2018, 140, 12695−12699). Because 1-Sc III and 1-Al III show 1 H NMR spectra essentially identical to that of [Mn III (OH 2 )(dpaq)] 2+ , the primary effect of these Lewis acids on 1 is protonation of the hydroxo ligand caused by an increase in the Brønsted acidity of the solution.