Structural Aspects of Alkyl and Aryl Metal Amides

STRUCTURAL ASPECTS OF ALKYL AND ARYL METAL AMIDES 

Whereas a considerable number of pure amides of Mg, Ca, and Ba are known, the alkyl or aryl amides of these elements have been little investigated (9). Compounds of the general formula RMgNR 2 are usually coordination polymers, unless ether molecules are added to the compound or bulky R 

As can be seen from the structure, the dimerization proceeds via nitrogen-magnesium interactions. To our knowledge, dimerization via Mg—R—Mg two-electron three-center bonds in alkylmagnesium amides has neither previously been found in the solid state nor proved by X-ray techniques, although the existence of such bonds has been claimed (10). 

The existence of alkyl- or aryl calcium amides has not as yet been unambiguously demonstrated. One reason for this seems to be because calcium— carbon bonds are much less stable than calcium—nitrogen bonds, as is illustrated by the following reaction [Eq. (2)] (12). 

PhjCCaCI 2THF + R2NH - R2NCaCI + Ph3C—H + 2THF (2) 

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