Grignard reagents, addition compounds

Initiation presumably involves metal alkyls as the primary source of carbanions. These are immediately available from the Grignard reagents, organosodium compounds, or sodium amide used as catalysts when the alkali metal itself or its solution in liquid ammonia is used, addition to the monomer may precede actual initiation. ... 

SCHEME 2. A termolecular mechanism for Grignard reagent addition to carbonyl compounds via... 

In contrast to Grignard reagents, dialkylzinc compounds are inert to carbon monoxide at atmospheric pressure either in the absence of solvents or in solution in THF, diglyme, ether, or benzene. Although Rathke and Yu reported in 1972 that the addition of potassium tert-butoxide in stoichiometric amounts promoted the absorption of carbon monoxide, it is now known that the actual reactive species was the corresponding zincate compound (R2ZnO-t-Bu) K+. The only zinc carbonyl species reported so far has been observed by NMR studies of CO on zeolite ZnY and poly crystalline ZnO, at low temperature. " Before this report, such species were only suggested from infrared and photoelectron studies of CO weakly bound to ZnO. 

The main use of organocadmium compounds is for the preparation of ketones and keto-esters, and their special merit lies in the fact that they react vigorously with acid chlorides of all types but add sluggishly or not at all to multiple bonds (compare addition of Grignard reagents to carbonyl groups). Some t3rpical syntheses are ... 

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