Manganese complexes olefins

Other cyclic olefine-manganese tricarbonyl complexes were investigated by Whitesides and Lichteriberger (64), and include (77schd)Mn(CO)3,0 sced)Mn(CO)3, and (i7scet)Mn(CO)3. In all three complexes, the ionizations of the six d-electrons fall at 8 eV, giving rise to a broad band, while 7r orbitals of the cyclic ligands produce two bands, at 8.5 and 10 eV. 

The synthesis of the manganese(III) complex of the hexaaza macrocyclic ligand (176), derived from 2,3-butanedione and diethylenetriamine, and its use as a catalyst for the epoxidation of olefins using iodosylbenzene as oxidant has been reported." ... 

The first metal-olefin complex was reported in 1827 by Zeise, but, until a few years ago, only palladium(II), platinum(Il), copper(I), silver(I), and mercury(II) were known to form such complexes (67, 188) and the nature of the bonding was not satisfactorily explained until 1951. However, recent work has shown that complexes of unsaturated hydrocarbons with metals of the vanadium, chromium, manganese, iron, and cobalt subgroups can be prepared when the metals are stabilized in a low-valent state by ligands such as carbon monoxide and the cyclopentadienyl anion. The wide variety of hydrocarbons which form complexes includes olefins, conjugated and nonconjugated polyolefins, cyclic polyolefins, and acetylenes. 

Attempts to prepare 64 from the tricyclic valence isomer of OFCOT afforded only the simple olefin complex 67, analogous to the manganese compound described above, and no subsequent ring opening could be effected (see... 

In order to increase the yield and/or the enantioselectivity of the reaction, the reaction temperature and additives were examined. Although aziridination was found to proceed smoothly at 0 °C, the product was not obtained at lower temperatures. Katsuki and co-workers have reported that pyridine /V-oxide is an effective additive for the asymmetric epoxidation catalyzed by salen-manganese(IH) complexes [24], and applied these findings to the asymmetric aziridination of olefins with Phi = NTs [9f]. Thus, the addition of pyridine /V-oxide at 0°C improved the enantioselectivity and allowed the reaction to proceed even at -20 °C (Table 6.1). Other additives, such as 4-phenylpyridine IV-oxide, 4-methylmorphorine N-oxide and 1-methylimidazole were used in the place of pyridine JV-oxide, but positive effects were not observed. 

The report by Kochi and co-workers in 1986 that a (salen)manganese(lll) complex (Mn(salen) complex) was an efficient epoxidation catalyst for simple olefins <1986JA2309> quickly led to independent reports from the groups of Jacobsen <1990JA2801> and Katsuki <1990TL7345> that chiral Mn(salen) complexes could catalyze asymmetric epoxidation reactions. The reaction requires the use of a stoichiometric oxidant initially iodosylarenes were utilized, but it was quickly found that NaOCl was also successful. 

Srinivasan, K., Michaud, P., Kochi, J. K. Epoxidation of olefins with cationic (salen)manganese(lll) complexes. The modulation of catalytic activity by substituents. J. Am. Chem. Soc. 1986, 108, 2309-2320. 

Irie, R., Noda, K., Ito, Y., Katsuki, T. Enantioselective epoxidation of unfunctionalized olefins using chiral (salen)manganese(lll) complexes. Tetrahedron Lett. 1991, 32, 1055-1058. 

G. Yin, M. Buchalova, A. M. Danby, C. M. Perkins, D. Kitko, J. D. Carter, W. M. Scheper, D. H. Busch, Olefin oxygenation by the hydroperoxide adduct of a nonheme Manganese(lV) complex Epoxidations by a metallo-peracid produces gentle selective oxidations, /. Am. Chem. Soc. 127 (2005) 17170. 

Epoxidation of Olefins Catalyzed by Manganese Hangman Complexes."... 

The likely mechanism of the CA[Mn]-catalyzed epoxidation of olefins is similar to that proposed by Burgess for free manganese involving peroxycarbonate as the key intermediate [41, 43 5], CA[Mn] forms a stable manganese-bicarbonate complex in the active-site [60], Hydrogen peroxide may add to carbonyl of this bicarbonate complex and displace water thereby forming a peroxycarbonate, which then may epoxidize a bound olefin. In contrast, heme peroxidases catalyze epoxidations either by a radical mechanism or by a ferryl-oxygen transfer mechanism [55]. 

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