ORGANOSILICON CHEMISTRY - FROM MOLECULES TO MATERIALS

The transition from basic to applied organosilicon chemistry is described for the research fields that are studied by the author's group: silaethene chemistry, organosilicon polymer chemistry with silacycles and the chemistry of higher coordinated silicon species. Early investigations started with the study of the pyrolysis of silacyclobutanes that yielded silaethenes in the gas phase. However, these investigations are tedious and are of little use for a widespread study of silaethene chemistry. Therefore the generation of silaethenes in solution (from vinylchlorosilanes and tert-butyllithium) is the preferred method. Numerous differently substituted silaethenes have been generated in situ and their reactivity, especially in cycloaddition reactions, has been studied. Silaethenes that have two chlorine substituents at the silicon atom (especially Cl2Si=CHCH(2)Bu(t)) show an unusual cycloaddition reactivity and yield unexpected pro ducts with dienes and trienes (e.g. from [2+2] and [6+2] reactions); some of the silenes with donorfunctional groups at the alpha undergo interesting intramolecular rearrangements. The cycloadducts of Si-dichlorofunctional silenes also show rearrangements when thermolyzed (e.g. [2+2] -->, [4+2] adducts). The reactivity of these silaethenes and their cycloadducts is due to the two chlorine atoms at the silicon atom and their influence can be explained by theoretical models. Silacycles synthesized from silaethenes have been incorporated or have been transformed into silicon containing polymers. Model compounds for nucleophilic substitution reactions at silicon centers and for the hydrolysis of chlorosilanes are higher coordinated silicon species up to coordination number ,,seven''. Some structures that describe such reactions have been characterized by X-ray crystallography.