Bonding strength anion

The most probable valence for the external bonds of an anion is called the anion bonding strength, 5a, and is defined by eqn (4.1)  

---

Fig. 4.2. Comparison of cation and anion bonding strengths for selected ions.

One can calculate cation bonding strengths, s, in the same way as anion bonding strengths by dividing the valence (or formal ionic charge) of a cation by its ideal coordination number, (eqn (4.2)) ... 

This chapter focuses primarily on the influence of anion-anion repulsion and on the anion bonding strength. The other factors are described briefly in Section 6.4 but are developed in more detail in later chapters. The special case of is discussed in Chapter 7 and effects that depend on details of the electronic structure of the cation are treated in Chapter 8. The influence of space and symmetry are discussed in Part III. For simplicity, unless otherwise stated, the discussion is confined to compounds in which the anion is oxygen or an oxyanion. Any conclusions will be applicable, mutatis mutandis, to other kinds of anion. 

In Section 4.5 it was shown that the bonding strengths of soft cations are less well defined than those of hard cations since they are able to form stable compounds with anions having a wider range of anion bonding strengths. Consequently they also display a wider range of coordination numbers. Thus the soft Zn + cation is found in four and six coordination in contrast to the similar, but hard, cation which is usually found only in 6-coordination. Most hard... 

Fig. 6.5. Coordination number versus anion bonding strength for Zn The areas of the...

Fig. 8.5. T1+ coordination number versus anion bonding strength. The curved line represents the coordination number expected if the valence of the Tl-O bonds is equal to the anion bonding strength. The circles are observed coordination numbers. The vertical lines mark the primary coordination number (bottom arrows) and the total coordination number (top arrow) for environments that contain both primary and secondary bonds.

The ester RO2R can be thought of as the compound formed from the Lewis base, RO2, and the Lewis acid, R " ", and its stability will be determined by the similarity of their cation and anion bonding strengths. 

Fig. 13.5. Free energy of hydrolysis versus the raiton of cation to anion bonding strength. Ac = acetyl, acetate, Ph = phenyl, Et = ethyl, ATP = adenosine triphosphate.

---