Poly(iminoborane)s with Aromatic Side Groups: Insights into the Microstructure from Monodisperse Model Oligomers

While certain inorganic main‐group polymers such as silicones (polysiloxanes) are ubiquitous in our everyday life, poly(iminoborane)s have been elusive for a long time. Incorporation of heterocyclic building blocks into their backbone has recently enabled access to the first derivatives of this inorganic‐polymer class, as this approach effectively prevents undesired side‐reactions to borazines. Information about the microstructure of these cyclolinear macromolecules, however, has been scarce. Herein, we present the synthesis of a series of monodisperse oligomers with up to 7 boron and 8 nitrogen atoms, representing the longest well‐defined molecular [>B=N<]x chain to date. We accomplished to characterize six of them structurally in the solid state by single‐crystal X‐ray diffraction, thus providing valuable insight into the microstructure of poly(iminoborane)s. In addition, we report on the synthesis of new poly(iminoborane) derivatives featuring aryl side groups, with an increased content of unsubstituted phenyl groups. The p‐(n‐butyl)phenyl‐substituted species 13 represents the highest‐molecular‐weight sample of this class of inorganic polymers to date.