Structure and reactivity of a mononuclear non-haem iron(III)-peroxo complex.
Oxygen-containing mononuclear iron species--iron(III)-peroxo, iron(III)-hydroperoxo and iron(IV)-oxo--are key intermediates in the catalytic activation of dioxygen by iron-containing metalloenzymes. It has been difficult to generate synthetic analogues of these three active iron-oxygen species in identical host complexes, which is necessary to elucidate changes to the structure of the iron centre during catalysis and the factors that control their chemical reactivities with substrates. Here we report the high-resolution crystal structure of a mononuclear non-haem side-on iron(III)-peroxo complex, [Fe(III)(TMC)(OO)](+). We also report a series of chemical reactions in which this iron(III)-peroxo complex is cleanly converted to the iron(III)-hydroperoxo complex, [Fe(III)(TMC)(OOH)](2+), via a short-lived intermediate on protonation. This iron(III)-hydroperoxo complex then cleanly converts to the ferryl complex, [Fe(IV)(TMC)(O)](2+), via homolytic O-O bond cleavage of the iron(III)-hydroperoxo species. All three of these iron species--the three most biologically relevant iron-oxygen intermediates--have been spectroscopically characterized; we note that they have been obtained using a simple macrocyclic ligand. We have performed relative reactivity studies on these three iron species which reveal that the iron(III)-hydroperoxo complex is the most reactive of the three in the deformylation of aldehydes and that it has a similar reactivity to the iron(IV)-oxo complex in C-H bond activation of alkylaromatics. These reactivity results demonstrate that iron(III)-hydroperoxo species are viable oxidants in both nucleophilic and electrophilic reactions by iron-containing enzymes.
Department of Bioinspired Science, Ewha Womans University, Seoul 120-750, Korea.
Jaeheung
J
Cho
Sujin
S
Jeon
Samuel A
SA
Wilson
Lei V
LV
Liu
Eun A
EA
Kang
Joseph J
JJ
Braymer
Mi Hee
MH
Lim
Britt
B
Hedman
Keith O
KO
Hodgson
Joan Selverstone
JS
Valentine
Edward I
EI
Solomon
Wonwoo
W
Nam
D000447:Aldehydes / Q000378:metabolism; D018360:Crystallography, X-Ray; D004798:Enzymes / Q000737:chemistry / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000737:chemistry* / Q000378:metabolism; D007501:Iron / Q000737:chemistry* / Q000378:metabolism; D008024:Ligands; D008958:Models, Molecular; D019159:Nonheme Iron Proteins / Q000737:chemistry / Q000378:metabolism; D010100:Oxygen / Q000737:chemistry / Q000378:metabolism
D000447:Aldehydes; D004798:Enzymes; D008024:Ligands; D019159:Nonheme Iron Proteins; D006861:Hydrogen Peroxide; D007501:Iron; D010100:Oxygen