Iron-oxygen bonds

The acid-catalyzed aquation of iron(III)-(substituted)oxinate complexes involves iron oxygen bond breaking and concomitant proton transfer in transition state formation. The latter aspect contrasts with the much slower acid-catalyzed aquation of hydroxamates, where proton transfer seems not to take place in the transition state. Reactivities, with and without proton assistance, for various stages in dissociation of a selection of bidentate and hexadentate hydroxamates, oxinates, and salicylates are compared and discussed—the overall theme is of dissociative activation. ... 

Nature of the Iron-Oxygen Bond and Control of Oxygen Affinity of the Heme by the Structure of the Globin in Hemoglobin... 

Pauling L, Weiss JJ (1964) Nature of iron-oxygen bond in oxyhaemoglobin. Nature 203 182-183... 

Tajima, K., K. Mikami, K. Tada, S. Oka, K. Ishizu, and H. Ohya-Nishiguchi (1992). Autoreduction of a six-coordinate iron(lll) tetraphenylporphyrin-peroxide complex by heterolytic iron-oxygen bond cleavage. Inorg. Chim. Acta 194, 57-65. 

Pauling, L. Nature of the iron-oxygen bond in oxyhae-moglobin. Nature 1964. 203. 182. 

By comparison, intramolecular chelation can be expected to reduce the degree of association of the catalyst. Addition of water results in increased association after hydrolysis of the ferric alkoxide. This may explain the effect of promoting stereoregularity by addition of water. The ferric alkoxide catalyst can also be made highly stereospecific by partial hydrolysis and still remain soluble in ether, the polymerization medium. This led to a suggestion that the catalyst may contain active Fe-O-Fe bonds. Such bonds would be formed from condensation of partially hydrolyzed alkoxide derivative. The monomer insertion between the iron-oxygen bonds can be illustrated as follows ... 

Theoretical consideration of stereoselective epoxidation with oxoiron porphyrins has lead to the remarkable conclusion that oxygen is inserted into the iron-nitrogen bond and the alkene is coordinated in a perpendicular orientation with respect to the iron-oxygen bond [64]. 

The Nature of the Iron-Oxygen Bond in Oxyhaemoglobin Nature 203, 182-183 (1964)... 

The problem discussed by Weiss, the nature of the iron-oxygen bond in oxyheemoglobin, was given a thorough discussion by me in two communications published about 15 years ago . It is now possible to amplify the discussion somewhat, in part because of further development of the theory of the chemical bond and in part because of the increased knowledge about the structure of oxy-hsemoglobin and related molecules that has been obtained by the X-ray diffraction investigations of Kendrew and Perutz . 

The nature of the iron-oxygen bond in oxyhemoglobin. Nature 203 (1964) ... 

The similarities and differences between iron-NO and iron-oxygen bonding have been the subjects of debate, and model compounds provide important correlations between structure, spectroscopy, and redox chemistry of iron nitrosyls. The nitrosyl groups in these complexes can be described as NO S = 0), NO S = 1/2), NO S = 0), NO (S = 1), and NO S = 1/2). The associated iron ions have charges and spins such that the overall numbers of iron d electrons plus NO Jt electrons are 6-8 in most experimentally accessible model compounds. The notation for these complexes follows the Enemark and Feltham conventions [51]. The EPR visible complexes are d , or (Fe-NO) , and d , or (Fe-(NO)2). Both S = 3/2 and S = 1/2 d complexes are found. Table 2 summarizes possible electronic states that might be considered for d iron-nitrosyl complexes. Representative references to those electronic states that are experimentally observed, or calculated, are given in the table footnotes. 

The main peak at 6.5 eV is composed of both oxygen 2p and iron 3d states, which indicate the presence of iron-oxygen bonds. The peak at 10.8 eV arises from the OH groups of chemisorbed water. This was established by drying a slurry of magnetite in water, inside the UHV system. This assignment is also in agreement with literature data of other hydroxide systems. ... 

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