Nickel complex main group

Nickel halides and nickel complexes resulting from oxidative addition can also give rise to subsequent replacement and insertion reactions. Replacement reactions have been described mainly with arylnickel halide complexes (examples 23, 29, and 31, Table III). Carbanionic species replace halide ions and can undergo coupling or insertion reactions. An example of application of a carbanionic reaction to the synthesis of a natural product is the coupling step between an aromatic iodo-derivative and an active methylene group to form cephalotaxinone (example 23, Table III). 

The main advantage of this procedure is that reactions occur at relatively high potential values, thus allowing the presence of sensitive functional groups on the starting material. In the presence of a nickel complex as catalyst, the process can be summarized as depicted in Scheme 3. 

This result emphasizes the role of interstitial atoms in determining the electronic structure and the properties of these materials. The NigCe core of the cluster can be regarded as a microscopic fragment of a nickel carbide. The interstitial main group atoms form strong bonds with the surroundings these bonds may be viewed as initial step in the formation of a different phase (carbides, nitrides, etc.) within the cluster complex. 

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