Simple meials

The function of the metal ions in Ihc reactions listed is lo attract electrons from the substrate. When this elTex t takes the form of simple polarization of the functional groups of the substrate, charge variations and electron shifts in these groups facilitate the chemical reactions listed under solvolysis and acid catalysts. When the meial ion removes completely one or more electrons from the substrate, the first step in an oxidation reaction occurs. 

The proposed reaction mechanism (see Scheme 4) is similar to that which is well established for olefin reduction, with the insertion of a meial-hydride bond into the carbonyl group coordinated to (he metal center. A mechanism in which reduction occurs by a simple nucIcopliiUc attack of the hydrogen atom of the transition metal hydride (which behaves like Blit or AlHa ) into the carbonyl group of the aldehyde, cannot be ignored ... 

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