Manganese system

DR. SUTIN I think that this is always a problem with exchange reactions involving aquometal ions. The manganese system bears out what Dr. Taube said we have to be sure of the numbers which we are attempting to interpret. In this regard, I believe that the manganese self-exchange rate constant which you referred to was not measured directly. 

Complex 27 is an isolobal analog of the manganese system 11 and like the latter exhibits rather large Si-H coupling constant of 80 Hz compared with the range... 

Scheme 4,11 Generation of carbonyl yUdes with a manganese system.

Applying the foregoing thermodynamic and kinetic information to manganese behavior in natural water systems is considerably limited because the manganese system exemplifies the difficulties discussed earlier. On the thermodynamic side, the kinds of oxide phases in natural waters may not correspond to those for which equilibrium data are available. Also, cation exchange reactions are probably important (21). On the kinetic side, the role of catalysis by various mineral surfaces in suspension or in sediments is not really known. Of considerable importance may be microbial catalysis of the oxidation or reduction processes, as described by Ehrlich (7). With respect to the real systems, relatively... 

The 1.5 V lithium iron sulfide system competes directly with the alkaline manganese system for high-performance electronic applications. It gives better high-rate performance than the alkaline manganese system. The other main commercial systems are the 3 V lithium carbon monofluoride (Li-CFx) system, and the lithium manganese dioxide (Li-Mn02) system. 

The Li-Mn02 cells are used for memory protection and to power smoke detectors, watches, and cameras. Although the manganese system has lower energy storage, it is less expensive and is preferred in commerce. 

Further Developments of Methodology 2.4.1. Understanding the Manganese System. 

It is intriguing to note that the colours of green KMn(CN)3 and tan K sMn(CN)3 are the reverse of what one might expect from parallels in the iron Prussian blue system KFe(CN)3 or Fe Fe CN) ] is colourless, whereas K jFefCN or KFe [FeIII(CN)6] is deep blue because of an interoxidation-state electron-transfer band. Clearly, further detailed study of these manganese systems is required, and the final explanation will probably need to take account of the availability of the MnIV state—note especially the tendency, under some conditions, for [Mn "(CN)6]3- to disproportionate to Mn11 and Mniv. 

The few vanadium-based studies present in the literature are summarized briefly here and, as with the manganese systems, they focus on the identification of key Intermediates in vanadium-catalyzed oxidations. These cases readily Illustrate the importance of considering both the positive and negative ion modes of ESl-MS when probing reaction mixtures. 

Althou less relevant as a model, [Mn(TPP)Q] is a better reagent for alkane oxidation and up to 70% conversion has been reported for cyclohexane in CH2Q2- Rearrangements were observed for norca-rane, which led to 7 products, including ones in which the CHjCh solvent had been incorporated. Meunier was the first to show that the far cheaper reagent, hypochlorite, could also be used to oxidize the manganese system. ... 

Encouraging re ul) have aJ o been obtained by A. L. Dem with cobalt manganese and tron manganese systems (138]. Ethylene selectivities of 45% could be observed with the Co/Mn system. 

In the case of silver-modified manganese systems, recent studies agree that the addition of silver increases the activity of methane oxidation, both in the case of Ag-Mn composite catalysts and Ag modified Mn02 catalysts (35,36). Silver-manganese-lanthanide oxide catalyst systems also were shown to be highly active, and recent studies suggested the reasons for this high activity (37). 

A comparison of the behaviour of manganese species with that of iron species is essential in any consideration of Eh-pH relationships in aqueous systems. The formation of insoluble, higher valency forms of iron in mixed iron-manganese systems, for instance, results in the disappearance of Mn(ll) from solution under Eh-pH conditions where this normally would not be predicted. 

The use of Ru catalysts for selective epoxidations has also been explored. The Ru(2,6-Cl2TPP)CO catalyst with dichloropyridine A-oxide as the stoichiometric oxidant provides good levels of stereocontrol for the synthesis of threo-dimm epoxides, 4 <05MI29>. The use of the manganese system, Mn(2,6-Cl2TPP)Cl, on amine 3 provides a 1.4 1 mixture of the 4-erythro 4-threo isomers in 88% yield after 1 hour <05JOC4226>. 

D+ = Ru(bpy)3+, Mn04, IO4, Pb02, etc.) catalysed by homogeneous catalysts (Co2+, Mn++ generated in situ). The kinetics and mechanism of manganese system Mn2+/ MnO " has been investigated in detail as a suitable model for the role of Mn in photosynthesis. 

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