High-resolution 15N solid-state NMR investigations on borazine-based precursors

Reference compounds based on borazine units and polyborylborazines have been characterized by N-15 solid-state NMR. The various nitrogen sites (B3N, B2NH, B2NX (X = H, Me, Pr-i), BN(H)X and BNX2 (X = Me, Pr-i) have been discriminated according to their cross-polarization behaviour and chemical shift values, which range from -265 to -350 ppm. This has permitted the elucidation of the polymerization mechanism associated with the polycondensation of two borazine-based derivatives. In particular, this technique appears to be a powerful investigation tool for finding whether the B3N3 rings are linked through three-atom N-B-N aminoboryl bridges or connected by direct B-N bonds. Copyright (C) 2004 John Wiley Sons, Ltd.