Metal-peroxo versus metal-oxo oxidants in non-heme iron-catalyzed olefin oxidations: computational and experimental studies on the effect of water.
Computational and experimental studies show that Fe(BPMEN)-catalyzed olefin oxidation has two (FeIII-OOH and FeV=O) oxidant species, which act with comparable activation barriers. The presence of water favors formation of an HO-FeV=O oxidant via water-assisted O-OH bond cleavage and leads to both epoxide and cis-diol products. In the absence of water, the oxidant is the FeIII-OOH [or (MeCN)FeIII-OOH], and oxidation mainly leads to epoxide. This conclusion differs from that derived from DFT investigations of iron-porphyrin-catalyzed olefin epoxidation, where the FeIII-OOH pathway is deemed too high in energy to be plausible. The difference between these two systems may lie in the more flexible coordination environment of the non-heme iron complex, which has an available adjacent coordination site that contributes to the activation of the peroxide in both wa and nwa pathways.
Quiñonero
David
D
Cherry L. Emerson Center for Scientific Computation and Department of Chemistry, Emory University, 1515 Dickey Drive, Atlanta, GA 30322, USA.
Morokuma
Keiji
K
Musaev
Djamaladdin G
DG
Mas-Ballesté
Rubén
R
Que
Lawrence
L
D000475:Alkenes / Q000737:chemistry*; D040761:Biomimetic Materials / Q000737:chemistry; D004852:Epoxy Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D005290:Ferric Compounds / Q000737:chemistry*; D019159:Nonheme Iron Proteins / Q000737:chemistry; D016877:Oxidants / Q000737:chemistry*; D010084:Oxidation-Reduction; D010087:Oxides / Q000737:chemistry*; D010105:Oxygenases / Q000737:chemistry
D000475:Alkenes; D004852:Epoxy Compounds; D005290:Ferric Compounds; D019159:Nonheme Iron Proteins; D016877:Oxidants; D010087:Oxides; D010105:Oxygenases