Short survey of network interactions

While covalent and coordinative bonds and intermolecular interactions are thoroughly covered in all sorts of textbooks and more advanced text, we will nevertheless make a short survey of them here. The reason is their paramount importance for our conception of nets, and the more general role they play in 

We will not waste much time on covalent bonds, they are well known to the chemically educated reader. However, it may be prudent to point out two things first, there are still a considerable number of elements in the periodic table that have never been connected to each other by a covalent bond, or where the examples are very few. In such cases there are no accepted definitions of normal bond lengths and angles, and controversy may result when proposing such bonds.  

Secondly, the formation of covalent bonds is usually irreversible (but see below) and proceeds through transition states and meta-stable intermediates with very different geometry from the starting material and product. For example, in nucleophilic substitution reactions on sp carbons we begin and end with a tetrahedral geometry while in-between we may have either triangular planar or penta-coordinated geometries. This may have dire consequences for 

There is a well-known definition of supramolecular chemistry as the chemistry of the non-covalent bond , and a lot of supramolecular chemistry has been done using coordination chemistry and the coordinative bond. However, it has been pointed out, [10] and is clear from most textbook treatment of ligand field theory, [11] that this is contradictory the coordinative bond is indeed a covalent bond. 

However, there are good reasons for treating this type of bond separately. One is that this bond is often reversible, that is there are low energy barriers for bond breaking and bond formation. This is however not always the case, and for some metal ions in certain oxidation states bond forming and breaking is extremely slow, for example the [Ir(H20)6] ion has the slowest self exchange kinetics of any homoleptic mononuclear metal centre with a half-life of coordinated waters of more than 3 years [12]. 

---