Manganese oxide, stereochemistry

A more long term goal is to explore the use of OMS and OL systems for other selective oxidations. Conventional manganese oxide reagents are typically used as oxidizing agents for stoichiometric oxidations on a laboratory scale. 51 Specific examples include oxidation of primary and secondary alcohols,10 transformation of vitamin A to retinene, l02 overoxidation of aldehydes to acids and esters, 03 etc. Radical intermediates and specific stereochemistries are important in these systems. We expect that these reactions can be carried out catalyticaiiy using our OMS and OL materials. 

Table 24.3 Oxidation states and stereochemistries of manganese, technetium and rhenium...

Monomeric species, with no exchange interaction between adjacent metal atoms, typically exhibit moments close to the spin only values. Most known compounds of manganese(II) and (III) are high spin, with the cyano compounds best known among the few low spin species. But these moments give no information about stereochemistry of the metal atom, and their purpose can be only to give information about the spin state and perhaps to help to confirm oxidation state. 

There still remains the question, which is unanswered by either the TT-bonding hypothesis or by the concept of metal polarizing power, as to why cobalt(III) and manganese(I) experience a cooperative ligand effect, whereas there is no evidence as yet for such an effect with chromium in various oxidation states [any Cr(III)—SCN compounds are purely kinetic in origin and thermodynamically unstable with respect to Cr(III)— NCS] with iron(II) or iron(III), cobalt(II), or nickel-(II), even though the stereochemistries of these last two elements may be drastically modified by ligational effects (see Tables XXIX and XXXI). 

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