Selective Oxidation of C-H Bonds through a Manganese(III) Hydroperoxo in MnII-Exchanged CFA-1.

Partial substitution of ZnII by MnII in Zn5(OAc)4(5,5'-bibenzo[d][1,2,3]triazole)3 (CFA-1) results in a MnII species supported by three nitrogen ligands and a charge-balancing anion, a structure reminiscent of those found in molecular "scorpionate" complexes. Unlike molecular manganese(II) scorpionates, Mn-CFA-1 is capable of catalytically activating oxygen from air to oxidize C-H bonds up to 87 kcal/mol in strength. A series of in situ spectroscopic studies, including diffuse-reflectance UV-vis, diffuse-reflectance infrared Fourier transform spectroscopy, and X-ray absorption spectroscopy, reveal that catalysis likely proceeds through a manganese(III) hydroperoxo that is only accessed in the presence of a hydrogen-atom donor. These results demonstrate that the site isolation provided in metal-organic frameworks enables the generation and utilization of highly reactive species for catalysis that are inaccessible in molecular systems.