Compounds with s, p and f Block Elements

Exploration of the potential applications of molecular mechanics to compounds of s-, p- and f-block elements is only just beginning. The difficulties arising from the electrostatic bonding in the s- and f-block elements have been tackled in a number of different ways, in most cases with reasonable success. In general, p-block elements are modeled relatively readily however, the problems of sterically active lone pairs have yet to be tackled. 

With the exception of polynuclear boron hydrides, cluster chemistry has developed mainly over the past 40 years. Prior to this a number of compormds that would now be classified as clusters had been but their nature was not recognized. It is perhaps interesting to ask the question of why cluster compounds, that is molecules containing metal-metal bonds, were considered prior to 1940 to be a relatively uncommon feature in inorganic chemistry The problem was in part associated with the dominance of organic chemistry coupled with the difficulties in the rapid determination of the structure of compounds of this type. The determination of the X-ray structure of relatively simple compounds could take months or years to accomplish. As stated above, for the s and p block elements the compounds were also generally found to be unstable to air and moisture, whilst for the d and f block the compounds were often very complex in structure and the stoichiometry difficult to assess. This led to a general lack of appreciation of the occurence and stability of metal-metal or element-element bonds. 

---