Intramolecular Interconversions in Cyclosilazane Chemistry: A Joint Experimental–Theoretical Study

Abstract

Publisher Summary The chemistry of cyclosilazanes and borazines is a topic of high interest in view of their importance for preceramic polymers. Rearrangement of cyclosilazanes is the first step of polymerization. To understand the polymerization processes of cyclosilazanes, fundamental research on the chemistry of this class of silicon rings is highly desirable. In comparison with other groups, silyl groups show great mobility. Silyl group migration depends on the propensity of the silicon atom to be bonded to the atom with the largest negative partial charge. Essentially, three types of interconversions are known: (a) Keto-enol tautomery, which is used in the synthesis of the first phoshaethenes and silaethenes; (b) Anionic isomerization; and (c) Neutral isomerization, which lead, for example, to the preparation of isomeric silylhydroxylamines and silylhydrazines. In ring systems, silyl migrations can lead to ring contractions or expansions. Of all the isomerization processes in inorganic ring systems, the interconversions in cyclosilazane chemistry are those that are presently best understood in terms of the mechanisms involved.