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[Fe II (MeCN) 4 ] 2+ (ClO 4 − ) 2 and [Fe III Cl 33 ] as Mimics for the Catalytic Centers of Peroxidase, Catalase and Cvtochrome P‐450
Author(s) -
Sawyer Donald T.,
Spencer Lee,
Sugimoto Hiroshi
Publication year - 1987
Publication title -
israel journal of chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.908
H-Index - 54
eISSN - 1869-5868
pISSN - 0021-2148
DOI - 10.1002/ijch.198800003
Subject(s) - chemistry , medicinal chemistry , catalysis , hydrogen peroxide , acetonitrile , electrophile , adduct , disproportionation , peroxide , reactive intermediate , peroxidase , stereochemistry , photochemistry , organic chemistry , enzyme
Addition of [Fe II (MeCN) 2 4 + (ClO − 4 ) 2 to solutions of hydrogen peroxide in dry acetonitrile (MeCN) catalyzes a rapid disproportionation of H 2 O 2 via the initial formation of an adduct, [Fe II (HOOH)↔Fe(O)(OH 2 )] 2+ , which oxidizes a second H 2 O 2 to dioxygen. This intermediate also cleanly oxidizes substituted hydrazines, alcohols, aldehydes, and thioethers by a two‐electron process. The products for these H 2 O 2 oxidations are consistent with those that result from catalase‐ and some peroxidase‐catalyzed processes. In the same aprotic medium (MeCN) anhydrous Fe III Cl 3 catalyzes the demethylation of N,N ‐dimethylaniline, the epoxidation of olefins, and the oxidative cleavage of 1‐phenyl‐1,2‐ethanediol (and other 1,2‐diols) by hydrogen peroxide. A mechanism is proposed in which an initial Lewis acid‐base interaction of Fe III Cl 3 with H 2 O 2 generates a highly electrophilic Fe III ‐oxene species as the reactive intermediate. For each class of substrate the products closely parallel those that result from their enzymatic oxidation by cytochrome P‐450. Because of (a) the close congruence of products, (b) the catalytic nature of the Fe III Cl 3 /H 2 O 2 reaction mimic, and (c) the similarity of the dipolar aprotic solvent (acetonitrile) to the proteinaceous lipid matrix of the biomembrane, the form of the reactive intermediate may be the same in each case. This is in contrast to the prevailing view that cytochrome P‐450 acts as a redox catalyst to generate an Fe(V)‐oxo species or an Fe(IV)‐oxo cation radical as the reactive intermediate.