Physical Manifestations of Nonbonded Interactions

Recent SCF—XaSW calculations indicate that the above geometry is stabilized by attractive ligand-ligand nonbonded interactions  

In the following sections, further experimental tests of nonbonded interactions will be discussed. Speciflcally, we shall examine the following topics  

In this section we shall determine the effect of nonbonded interactions on the physical properties of related molecules. As our model compounds we will utilize difluoroethylene, a molecule having substituents bearing only lone pairs and dicyano-ethylene, a molecule bearing substituents with both filled and unfilled MO s. In particular, we focus on the three possible isomers of a disubstituted ethylene ie. the 1,1, /ranj-1,2- and c/s-1,2-isomers. The three possible isomers are shown below. 

Overlap integrals calculated by a CNDO/2 program. Standard geometries. 

An analogous procedure can be applied to the dicyanoethylene. We can dissect the molecule into an NC—CN fragment and a HC=CH fragment. The appropriate interaction diagrams are shown in Fig. 37. A consideration of these dia ams leads to the following conclusions. 

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