High-valent

H-Oxocin-3-one, 2,3,7,8-tetrahydro-synthesis, 7, 667 Oxocins, 7, 668-669 47/-Oxocins synthesis, 7, 669 Oxocinyl anions aromaticity, 7, 669 Oxoiron compounds high valent... 

High-valent ruthenium oxides (e. g., Ru04) are powerful oxidants and react readily with olefins, mostly resulting in cleavage of the double bond [132]. If reactions are performed with very short reaction times (0.5 min.) at 0 °C it is possible to control the reactivity better and thereby to obtain ds-diols. On the other hand, the use of less reactive, low-valent ruthenium complexes in combination with various terminal oxidants for the preparation of epoxides from simple olefins has been described [133]. In the more successful earlier cases, ruthenium porphyrins were used as catalysts, especially in combination with N-oxides as terminal oxidants [134, 135, 136]. Two examples are shown in Scheme 6.20, terminal olefins being oxidized in the presence of catalytic amounts of Ru-porphyrins 25 and 26 with the sterically hindered 2,6-dichloropyridine N-oxide (2,6-DCPNO) as oxidant. The use... 

Table 12.2 Epoxidation of olefins with bis(trimethylsilyl) peroxide (BTSP) catalyzed by high-valent oxorhenium deri-vatives> bl...

Preparation and properties of high valent first row transition metal oxides and halides. C. Rosen-blum and S. L. Holt, Transition Met. Chem. (N.Y.), 1972, 7,87-182 (303). 

It is found that chromium atoms, manganese atoms, and tin atoms exist in metals in two forms, a small, high-valent form and a larger, low-valent form. The two kinds of manganese atoms coexist in a-manganese and in /3-manganese. 

High-Valent Complexes of Ruthenium and Osmium Chi-Ming Che and Vivian Wing-Wah Yam... 

Abstract In this review, recent developments of iron-catalyzed oxidations of olefins (epoxidation), alkanes, arenes, and alcohols are summarized. Special focus is given on the ligand systems and the catalytic performance of the iron complexes. In addition, the mechanistic involvement of high-valent iron-oxo species is discussed. 

Because there exist a number of reviews which deals with the structural and mechanistic aspects of high-valent iron-oxo and peroxo complexes [6,7], we focus in this report on the application and catalysis of iron complexes in selected important oxidation reactions. When appropriate we will discuss the involvement and characterization of Fe-oxo intermediates in these reactions. 

Remarkably, the shown Fe ° complexes reacted directly with oxygen to afford high-valent oxo-iron species. In addition, Kim, Nam, and coworkers explored... 

High-valent iron-imido complexes have also been proposed as reaction intermediates in several reactions of the iron catalysis. Que and coworkers have provided evidence for Fe(IV) imide as a reaction intermediate in the reaction of [(6-PhTPA)-Fe°(CH3CN)2] " with PhI=NTs. Borovik and coworkers have also reported the formation of an amide product involving the generation of a putative iron(IV) imide [36] (Scheme 7). 

Watanabe Y. 2000. High-valent intermediates. In Radish KM, Smith KM, Guilard R, editors. The Porphyrin Handbook. San Diego Academic Press, p. 97. 

Fig. 5.9 A simple model for a high-valent Fe(IV) system [FeOfNHals] (see [60])...

High-valent iron can occur in a wide variety of electronic configurations. Figure 8.25 (a-c, e-i) presents a summary of the corresponding one-electron crystal-field states for the 3(/, 3J, and 3J electron configurations, allocated to HS and LS states in distorted octahedral and tetrahedral symmetry. Part d, in addition, depicts the case of low-low-spin iron(IV) found in some trigonal... 

High-valent iron also occurs in -nitrido bridged dimers with linear [Fe °-N=Fe" ]" and [Fe =N=Fe ] " cores [209, 210] (and references therein). Such compounds have been prepared first by thermolysis [247] or photolysis [248] of iron(III)-porphyrin complexes with an azide ligand, (N3). Mixed-valent iron-nitrido porphyrin dimers exhibit valence delocalization as can be inferred from the... 

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