Manganese bromide

Mid-Century Also called M-C. A process for oxidizing p-xylene to terephthalic acid, using oxygen in acetic acid and catalyzed by a mixture of cobalt and manganese bromides. Developed in the 1950s by Halcon International and commercialized by Standard Oil Company (Indiana). The first plant was built at Jolet, IA, in 1938. The Amoco and Maruzen processes are improved versions. 

Manganese borates, 4 282 Manganese boron, 4 136 Manganese bromide, physical properties of, 4 329... 

Different primary, secondary aryl or heteroaryl manganese bromides 519 were prepared by reaction of activated manganese [prepared form manganese dichloride, lithium and a catalytic amount (15%) of 2-phenylpyridine as electron carrier, in THF] with the corresponding brominated compounds 516. These intermediates react with different electrophiles in THF at 0°C with or without copper chloride, to yield the corresponding products 20 (Scheme 144). ... 

Manganese Pyrovanadate, MnaV207, is obtained in large, brilliant brown needles by fusing together a mixture of vanadium pentoxide, sodium bromide and manganese bromide.4... 

Synthesis of unsymmetrical sec- and tert-alcohols. An attractive route to these alcohols involves a one-pot acylation (13,210) of RMnBr followed by reaction with an alkyllithium (14, 229). The overall yield is generally higher than that obtained by reaction of the alkyllithium with the isolated, intermediate ketone. An example is the synthesis of a-bisabolol (2) from the homoallylic manganese bromide 1. These RMnBr reagents can be prepared from RLi using MnBr2, which... 

Commercially two main processes, that of Mid-century/Amoco and Dynamit Nobel/Hercules, are operated. In the former acetic acid is used as a solvent. Mixtures of cobalt and manganese bromide and acetate salts are used to catalyze the initiation step. The reaction conditions, a temperature of about 220°C and a pressure of 15 atm, are relatively severe. Under these conditions bromine and CH2C02H radicals are formed. These radicals can effect new initiation steps. In the overall process, though toluic acid is an intermediate, it is never isolated. The final isolated product is terephthalic acid (see reaction 8.10). 

Dicyclopentadienyl manganese was first obtained by thermal decomposition of the ammine [MnfNHsle] (CbHb)2 (50, 111). Shortly afterward, it was made in good yield by the reaction between manganese bromide and cyclopentadienyl sodium in tetrahydrofuran (214), and it may also be prepared by the interaction of manganese chloride and an ethereal solution of the Grignard reagent, followed by sublimation (60). At ordinary temperatures it forms brown crystals. 

Transformation of 4-methylpyrazoles into 4-carboxylic acids takes place readily by cobalt-manganese bromide mediated oxidation <91CL585>. Begtrup <92JCS(P1)2555> has developed a method to activate methyl groups at positions 3 and 5 using 2-alkoxy-pyrazohum derivatives (181) in this way pyrazoles (182) were prepared (X = D, I, OMe). 

Oxidation of the bipyridyl tetracarbonyl derivatives of molybdenum and tungsten affords seven-coordinate derivatives of the dipositive metals (662), e.g., the compound W(CO)3(bipy)(HgCl)2 contains tung-sten-to-mercury bonds (273). Compounds containingbidentateterpyridyl have been obtained from Cr(CO)e and Mo(CO)6 by reaction with terpyridyl in isopentane solution under the influence of UV light. Pentacarbonyl-manganese bromide affords the compound Mn(CO)3(terpy)Br (274) which has an infrared spectrum identical with that of Mn(CO)3(bipy)Br (1, 78, 242, 377). 

Diazenido complexes were isolated as products from the reaction of trimethylsilylphenyldiazene, Me3Si—N=N—Ph (instead of BSD), with cyclopentadienyltitanium trichloride (CpTiCl3) (74), or pentacarbonyl-manganese bromide [(CO)sMnBr] (75) [Eqs. (94) and (95)]. 

This chapter is not intended to be a comprehensive literature review, but instead presents the authors views that explain the key features of the chemistry and mechanism of cobalt-manganese-bromide-catalyzed oxidation of pX to TA, byproduct formation, and purification chemistry. An overview of the engineering aspects of the process and of the purification chemistry is also provided. 

Cobalt-Manganese-Bromide Catalysis (MC Oxidation) The Nature of Synergy between Co and Mn... 

Manganese-bromide m-[MnX2(CO)J- 1,2-dichloroethane -chloroform nitromethane 0-3 15... 

In the manganese-bromide system, the octahedral [Mn(AN)6]+ " ion is converted to a tetrahedral species by coordination of one bromide ligand to give [MnBr(AN)3]+. The other tetrahedral forms, [MnBr2(AN)2], [MnBrsAN] and [MnBr4] can be obtained by further addition of bromide ions to the acetonitrile solution 4 With chloride ions also tetrahedral species are produced but [MnClsAN]" has a low stability in acetonitrile. 

DMSO, but tetrachlorocobaltate(II) is capable of existence in this solvent, in which C0CI2 undergoes considerable autocomplex formation. Likewise manganese bromide is completely ionized in TMP, but MnCLa and [MnCU]"" are known to exist in TMP solutions again with autocomplex formation of MnCl2. 

The coupling reaction with phenyl isocyanate was also examined. The aryl-manganese bromide reagents underwent a coupling reaction with phenyl isocyanate without any transition metal catalyst to yield the corresponding amides in moderate yields (Table 8.6). 

While the oxidative addition of Mn prepared from manganese bromide and chloride to benzyl halides vras completed at rt in 20 min in THE (Scheme 8.5),... 

Table 8.10 Cross-coupling reaction of benzylic manganese bromide. ... 

Preparation of Heteroarylmanganese Reagents and Their Cross-Coupling Chemistry 357 Table 8.26 Reactions of heteroaryl manganese bromides with benzoyl chloride. 

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