TABLE OF CONTENTS The formation of cyclic oligomers and polymers with an inorganic backbone is an important subject of study, of both academic and applicative interest. Inorganic rings of various compositions and structures are well known and new ones are frequently described. Their chemistry has been reviewed in several monographs [1]. The inorganic rings raise interesting questions of structure and bonding and quite often they challenge the theory. Their applicative interest is related to their use as precursors for thermally stable polymers, ceramics, semiconductors, catalyst supports or various other advanced materials [2].
Inorganic chemistry displays a rich diversity of ring structures in terms of bond types. The obvious and most important are the cyclic molecules formed through covalent bonds. Inorganic ring structures can be built by catenation of identical atoms (inorganic homocycles) or by combining a number of various building blocks (synthons) made up from different elements, connected through covalent bonds.
Inorganic ring and polymer formation is not limited to covalent bonding. It can also be achieved by assembling supramolecular structures from molecular units (tectons) connected through noncovalent intermolecular forces (dative bonds, secondary bonds, ionic interactions or hydrogen bonds) [3]. This is the field of supramolecular chemistry and the spontaneous process leading to such structures is called self-assembly or self-organisation.
Since reference was made to supramolecular chemistry, perhaps it is useful to remember some definitions. Supramolecular chemistry is " the chemistry of molecular assemblies and...
