
%0 Journal Article
%A Brown, RD 
%A Harcourt, RD 
%T The Electronic Structures of A<sub>2</sub>Y<sub>4</sub> Molecules
%J Australian Journal of Chemistry
%D 1963/10/01
%V 16
%N 5
%P 737-758
%K 
%R https://doi.org/10.1071/CH9630737
%U https://www.publish.csiro.au/paper/CH9630737 
%X A study of the electronic structures of A2Y4 molecules containing 34, 36, and 38 valence electrons has been made. An approximate VESCF, molecular- orbital method was used, attention being concentrated mainly on the delocalization of &#963;-electrons which are classically regarded as lone-pairs on the Y atoms. The results provide explanations of the main features of many of the observed AA- and AY-bond lengths and YAY-bond angles of N2O4, C2O42-, B2F4, B2Cl4, C2F4, C2Cl4, S2O42-, and N2F4. Other A2Y4 systems which have either not been fully characterized or not yet reported are also considered.   The extent of lone-pair delocalization is shown to be governed by a parameter a&#963;, related to the coulomb and resonance parameters of Hückel molecular-orbital theory. General trends in the value of a&#963; can be predicted from values of the core charges of A and Y towards the o-electrons concerned. A more detailed &quot;adjacent charge&quot; rule emerges. It differs from the classical rule in that for A2Y4 systems, adjacent negative formal charges on the A atoms should not very greatly affect the AA-bond properties.   Difficulties were encountered in consistently interpreting the properties of some A2F4 and A2Cl4 compounds. These deserve further attention. 
