Equatorial Ligand Perturbations Influence the Reactivity of Manganese(IV)‐Oxo Complexes

Abstract

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MnIV-Oxo complex of a bis(benzimidazolyl)-containing N5 ligand reveals different reactivity trends for MnIV-oxo than FeIV-oxo species

“…The energy and intensity of the near-IR absorption band at 940 nm (ε = 250 M −1 cm −1 , assuming 100% formation) is quite similar to that observed for Mn IV -oxo complexes of the N4py, DMM N4py, and 2pyN2Q ligands (λ max = 920 -1180 nm; ε = 179 -290 M −1 cm −1 ; Table 2). 6,26 On the basis of this similarity, and strongly supported by additional data described below, we assign the chromophore formed by the reaction of and its derivatives showed that variations in the energy of this electronic transition arise predominantly from perturbations in Mn−N equatorial bonding. 6,29 As shown in Figure S5).…”

“…25 Analysis of the product of the reaction of [Mn IV (O)(2pyN2B)] 2+ and thioanisole was performed by 1 H-NMR experiments following previously described methods. 6 The only modification was the use of toluene as internal standard, which was added directly to the 1 H-NMR sample before analysis.…”

“…For example, we recently reported that Mn IV -oxo adducts supported by derivatives of the pentadentate N4py ligand display HAT and OAT reaction rates that are dependent on the equatorial ligand field strength (Figure 1). 6 The N4py derivatives previously considered were DMM N4py and 2pyN2Q (Figure 1), which respectively feature electron-rich di-3,5-methyl-4-methoxy-pyridyl groups and bulky quinolinyl groups that serve to increase (for DMM N4py) and decrease (for 2pyN2Q) the equatorial ligand field of the Mn center relative to the parent N4py ligand. A DFT structure of [Mn IV (O)(2pyN2Q)] 2+ showed that the steric bulk of the quinolinyl groups also crowds the oxo coordination position, causing a N axial −Mn=O angle of 170°, with the oxo ligand tilted away from the quinolinyl moieties ( Figure 1).…”

Oxidation of Naphthalene with a Manganese(IV) Bis(hydroxo) Complex in the Presence of Acid

“…Zuschriften most positive potential for all known nonheme Mn IV bis-(hydroxo) as well as Mn IV oxo intermediates. [35] Considering the highly positive reduction potential, we were interested in studying whether complex 2 could be employed for the oxidation of naphthalene.Upon addition of al arge excess of naphthalene to 2 (1.0 mm)i nas olvent mixture of CF 3 CH 2 OH/acetone (1:3 v/v) at À30 8 8C, however, 2 remained intact, and product analysis of the reaction solution confirmed that no products of naphthalene oxidation had been generated.…”

“…ET reduction of 2 was found to be in equilibrium with [Fe II (phen) 3 ] 2+ ,w here the final concentration of [Fe III -(phen) 3 ] 3+ produced in the ET of 2 increased upon increasing the initial concentration of [Fe II (phen) 3 ] 2+ .T he equilibrium constant (K et )w as determined to be 1.38, and the oneelectron reduction potential (E red )o f2 was then determined to be 1.09 Vv s. SCE using the Nernst equation (Figures S8 and S9). [35] Considering the highly positive reduction potential, we were interested in studying whether complex 2 could be employed for the oxidation of naphthalene.Upon addition of al arge excess of naphthalene to 2 (1.0 mm)i nas olvent mixture of CF 3 CH 2 OH/acetone (1:3 v/v) at À30 8 8C, however, 2 remained intact, and product analysis of the reaction solution confirmed that no products of naphthalene oxidation had been generated. [33] The inset shows an expansion of the pre-edge region from 6536 to 6546 eV.…”