Structures and Bonding in Group III Derivatives

A very brief summary of the salient points with regard to the structures, bonding, and their influence on the mechanisms of exchange and rearrangement process for aluminum and its heavier congeners follows, prior to the discussion of specific systems. The structures for several of the important aluminum derivatives are shown in 1-6. All of 

Structure of the heavier congeners of group III have not been as extensively investigated those that have been determined in the solid state do not have bridging alkyl or aryl groups, but are found to exist either as monomers or loosely associated aggregates 8, 39). The structures for these monomeric derivatives can be represented by 7 with 

Evidence for formation of dimeric gallium derivatives with bridging vinyl groups has been reported (40, 53), and both phenylethynylgallium and indium also have been shown to be dimeric (24). 

The bonding present within the bridged molecules can be treated in a simple manner, making use of two orbitals from the two metal atoms and one from the bridging group for each bridge bond. This is shown 

Construction of simple (although approximate) molecular orbital (MO) schemes from this system leads to an energy level diagram having three levels, bonding, nonbonding, and antibonding, as shown in 9a, 9b, and 9c. 

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