Structural studies, lead compounds electron pairs

Amides and related compounds have been thoroughly investigated as ligands for alkali metals. Studies in solution have been made using various physicochemical techniques these, and MO calculations, show that the interaction of amides with M+ is via the carbonyl function.56,57 This leads to a delocalization of the amide N electron pair and so it is possible to follow the decrease in C—O, and the increase in C—N, bond orders using IR spectroscopy. X-Ray crystal structures of amide complexes have shown both types of complexation interaction to be present (Table 2). 

In Table 10 the first three IPs of some substituted anilines are summarized. Aniline and other aromatic amines are systems weU suited for studies of substituent effects on the electronic structure and the effects of stoic inhibition to resonance - . Since such effects mainly affect the electronic structure of the benzene ring it would lead too far covering these compounds hoe in detail. However, a few remarks seem to be adequate. Because of the electron delocalization thoe are several MOs with substantial UN contributions. However, in most cases the third highest occupied MO (HOMO-2), or the third IP, is mainly related to the electron lone-pair. Thoefore, the assignment of the IPs is generally the same as for the parent molecules IPi and IP2 are assigned to 71 and Jt2, respectively, and IP3 is assigned to /in. 

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