1,2,5-Azadiborolane as a Building Block for Inorganic-Organic Hybrid Polymers

The incorporation of BN units in organic scaffolds by isoelectronic/isosteric substitution of selected CC couples has emerged as an efficient tool to produce new materials with useful properties and functions. The knowledge about BN-doped inorganic-organic hybrid polymers, however, is still rather scarce. This is especially true for linear or cyclolinear macromolecules that feature longer inorganic chains. Herein, we introduce 1,2,5-azadiborolane as a polymer building block for the first time. An attempt to apply it for the synthesis of a cyclolinear poly(iminoborane) resulted after only two B-N coupling events in the formation of a molecular compound comprising a chain of three nitrogen and two boron atoms - as confirmed by single-crystal X-ray diffractometry. In combination with a p-phenylene diamine-based co-monomer, we accomplished to incorporate the 1,2,5-azadiborolane into a hybrid polymer of considerable molecular weight that features a B2N3 chain. We additionally synthesized a small molecular model compound for the polymer and characterized it crystallographically as well. Comparison of the UV-vis spectra of the monomer, the oligomer, and the polymer revealed systematic red-shifts of the longest-wavelength absorption band with increasing number of BN units in the chain. 1,2,5-Azadiborolane is introduced as a new building block for BCN hybrid polymers. An attempt to use it as a monomer for a cyclolinear poly(iminoborane), only afforded two B-N coupling events. On the other hand, in combination with a p-phenylene diamine-based co-monomer, we obtained hybrid polymers with an average degree of polymerization exceeding 300.+image