Manganese alkyl, reaction

Whether coordination of the carbon monoxide is required before insertion can take place in all these examples is not clear. But since it is required in the alkyl-manganese pentacarbonyl reaction, it is not unreasonable to expect the same to be true in the other cases. 

Analogously, reaction of group 7 metal carbonyl anions M(CO)5 (M = Mn, Re) with MeC(CFFI), gave cyclopropylcarbinyl complexes. Flowever, whereas rhenium produces the normal (/-metal bonded cyclopropylcarbinyl complex, the manganese complex furnished (cyclopropylacetyl)Mn(CO)5, where carbonyl insertion into the manganese-alkyl bond occurred (equation 56)114. 

Reaction of [Mn(R)(CO)5] with cationic species often results in cleavage of the manganese-alkyl carbon bond. Thus, the reaction of [Mn(CH3)(CO)5] with sulfuric or hydrochloric acid produces methane (84) [Eq. (20)]. The reaction is believed to occur via oxidative addition of the acid followed by reductive elimination of CH4. 

Reactions 33 and 35 constitute the two principal reactions of alkyl hydroperoxides with metal complexes and are the most common pathway for catalysis of LPOs (2). Both manganese and cobalt are especially effective in these reactions. There is extensive evidence that the oxidation of intermediate ketones is enhanced by a manganese catalyst, probably through an enol mechanism (34,96,183—185). 

Unsymmetrical dialkyl peroxides are obtained by the reaction of alkyl hydroperoxides with a substrate, ie, R H, from which a hydrogen can be abstracted readily in the presence of certain cobalt, copper, or manganese salts (eq. 30). However, this process is not efficient since two moles of the hydroperoxide are consumed per mole of dialkyl peroxide produced. In addition, side reactions involving free radicals produce undesired by-products (44,66). 

Another important line of investigation concerned the carbonyl insertion reaction, which was best defined in manganese chemistry (75, 16) and extended to acylcobalt tetracarbonyls by Heck and Breslow. The insertion may be through three-membered ring formation or by nucleophilic attack of an alkyl group on a coordinated CO group. 

Acylation reactions can also be greatly improved in this way, with t-alkyl- or sec-alkyl-manganese reagents reacting with acid chlorides in excellent yields [123]. The related addition-elimination to 3-ethoxy-2-cyclohexenone is also improved, resulting after acidic aqueous workup in 3-methyl-2-cyclohexenone [125]. The perilla-ketone 126 was prepared in an improved yield using copper(I) catalysis (Scheme 2.58) [129]. 

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