HAA by the first {Mn(iii)OH} complex with all O-donor ligands.

There is considerable interest in MnOH moieties, particularly in the stepwise changes in those O-H bonds in tandem with Mn oxidation state changes. The reactivity of aquo-derived ligands, {MOH}, is also heavily influenced by the electronic character of the other ligands. Despite the prevalence of oxygen coordination in biological systems, preparation of mononuclear Mn complexes of this type with all O-donors is rare. Herein, we report several Mn complexes with perfluoropinacolate (pin) including the first example of a crystallographically characterized mononuclear {Mn(iii)OH} with all O-donors, K[Mn(OH)(pin)], 3. Complex 3 is prepared deprotonation of K[Mn(OH)(pin)], 1, the p of which is estimated to be 18.3 ± 0.3. Cyclic voltammetry reveals quasi-reversible redox behavior for both 1 and 3 with an unusually large Δ, assigned to the Mn(iii/ii) couple. Using the Bordwell method, the bond dissociation free energy (BDFE) of the O-H bond in {Mn(ii)-OH} is estimated to be 67-70 kcal mol. Complex 3 abstracts H-atoms from 1,2-diphenylhydrazine, 2,4,6-TTBP, and TEMPOH, the latter of which supports a PCET mechanism. Under basic conditions in air, the synthesis of 1 results in K[Mn(OAc)(pin)], 2, proposed to result from the oxidation of EtO to EtOAc by a reactive Mn species, followed by ester hydrolysis. Complex 3 alone does not react with EtO, but addition of O at low temperature effects the formation of a new chromophore proposed to be a Mn(iv) species. The related complexes K(18C6)[Mn(iii)(pin)], 4, and (MeN)[Mn(ii)(pin)], 5, have also been prepared and their properties discussed in relation to complexes 1-3.