Shape‐Selective Interception by Hydrocarbons of the O₂‐Derived Oxidant of a Biomimetic Nonheme Iron Complex

Abstract

Wählerisches Ferryl: [Fe(Tp Ph 2)(BF)] (Tp Ph 2=Hydrotris(3,5‐diphenylpyrazolyl)borat; BF=Benzoylformiat) liefert mit O2 ein Oxidationsmittel (siehe Bild; O rot, rosa, Fe gelb, N blau, C grau, H weiß), das Kohlenwasserstoffe formselektiv oxidiert. Die Ursache hierfür ist eine durch zwei Phenylgruppen des Tp Ph 2‐Liganden gebildete Spalte, die abgeflachte spheroidale Substrate bevorzugt.

Electronic Structure Analysis of the Oxygen‐Activation Mechanism by FeII‐ and α‐Ketoglutarate (αKG)‐Dependent Dioxygenases

“…[19] The structures of the model complexes show that the α-ketoacid can bind to the Fe II center in a mon odentate or a bidentate mode. [20] Comparison of the diagnostic metal-to-ligand charge-transfer transition of the enzyme/Fe II /αKG complexes to those of the model complexes indicates that αKG must be bound to the metal in a bidentate way at the enzyme active site.…”

“…The acceleration of decarboxylation caused by electron-withdrawing substituents on the α-ketoacid in the model complexes is in line with the proposed nucleophilic attack of the distal O atom derived from the oxygen on C2 of the α-ketoacid. [19b] Que and co-workers reported an excellent functional model compound for the αKG-dependent dioxygenases, [Fe(Tp Ph2 )(BF)] (Tp Ph2 =hydrotris(3,5-diphenylpyrazol-1-yl)borate, BF=benzoylformate). [19a,b] Upon reaction with O 2 , this complex is able to hydroxylate one of the phenyl rings of the Tp Ph2 ligand coupled with decarboxylation of the BF ligand, as confirmed by isotope labeling experiments; this reaction captures several of the salient features of the Fe II - and αKG-dependent enzymes, that is, decarboxylation of the coordinated α-ketoacid and generation of the ferryl intermediate.…”

The Frontiers of Organic Chemistry at the Bürgenstock Conference

“…Interestingly, the efficiency of the reaction proved not to be related to the strength of the CÀH bond, but to the shape of the molecule, which has to fit in the cavity provided by the catalyst (Figure 2). [4] That is why hydrogen abstraction occurred efficiently with cyclohexene but not with ethylbenzene, even though they posses CÀH bonds of similar strength.…”

Oxidative dehydrogenation of 5-(pyridine-2-yl-methyl)-2-thioxo-4-imidazolidinones in complexation reaction with copper(II) chloride

“…Desaturase reduces dioxygen to give the alkene. Only a few examples of transition metal complexes mimicking the desaturase function are described to date, including iron [11][12][13], manganese [14-16] and copper [17] complexes.We have recently report the synthesis and catalytical properties of mixed-valent dinuclear copper complexes of 3-phenyl-5-pyridylmethylene-2-thioxoimidazolidin-4-one [18]. We describe therein the unusual case of C-C to C_C bond conversion in the processes of Cu(II) complexation with 5-(pyridine-2-ylmethyl)-3,5-dihydro-4H-imidazole-4-ones.…”

“…Desaturase reduces dioxygen to give the alkene. Only a few examples of transition metal complexes mimicking the desaturase function are described to date, including iron [11][12][13], manganese [14-16] and copper [17] complexes.…”