Mechanistic and Kinetic Aspects of Transition Metal Oxygen Chemistry

Oxidative Homolysis of a Nitrosylchromium Complex

“…The complex [Cr aq OO] 2 + has been characterized spectroscopically and chemically. [26][27][28] OO] 2 + by metal polypyridine complexes of ruthenium and iron, [29] and will now use these data as a baseline against which the redox behavior of [Cr aq NO] 2 + will be gauged. It is advantageous for our purpose that the ligand system is identical in the nitrosyl and superoxo complexes.…”

Mechanisms of Oxygen Binding and Activation at Transition Metal Centers

“…14,21,31,32 Cobalt analogue of myoglobin, coboglobin, is a functional oxygen carrier. After the formation of the first bond, quite different consecutive steps can occur (Figure 4.6 illustrates possible pathways for iron complexes 17 ; other metals show analogous chemistry, although their exact oxidation states may differ).…”

“…The 2 : 1 stoichiometry of the Fe(TMC) 2 þ /O 2 reaction suggests a bimolecular mechanism with the intermediacy of diiron(III)-peroxo species, analogous to the mechanism of O-O bond cleavage by iron(II) porphyrins (see above). 14,15 For comparison, TiO 2 þ and VO 2 þ , which can be obtained from Ti(II) and V(II), respectively, do not display oxidizing properties; Mn IV ¼O and especially Mn V ¼O compounds are potent oxidants, but their plausible Mn(II) precursors are unreactive with O 2 (unless the metal is bound to strongly electrondonating ligands, such as corroles 64 ). Even though most other transition metals are not found in oxygen-activating enzymes, they can participate in similar reaction pathways and support similar intermediates in their reactions with dioxygen or oxygen atom donors.…”

“…The literature on oxygen activation is extensive, including books, [5][6][7][8][9] chapters, 2,10 journal special issues, [11][12][13] review articles, [14][15][16] and numerous primary publications; only a handful of representative references are cited above. A comprehensive review of this active area of research is nearly impossible, and definitely beyond the scope of this work.…”

Solvent-free oxidation of alcohols by hydrogen peroxide over chromium Schiff base complexes immobilized on MCM-41

“…Therefore, clean, inexpensive oxidants such as molecular oxygen or hydrogen peroxide have increasingly been adopted in alternative routes. However, the addition of dioxygen to hydrocarbons generally requires high activation energies due to the high energy needed to break the O-O double bond and the spin mismatch between the ground state of O 2 (triplet) and organic reductants (singlet) [3][4][5]. This greatly enhances the potential of hydrogen peroxide, especially at low concentrations as an oxidant.…”