PREPARATION AND CHARACTERIZATION OF POLYBORAZINES

The reaction of the borazine (C2H5)3B3N3H2[Si(CH3)3] with B-monohaloborazines gives reasonable yields of diborazinyls (C2H5)3B3N3H2[R2B3N3R3'] (1); in addition, small amounts of polyborazinyls (2,3) are formed and species containing up to four borazine rings in an individual molecule could be identified. The triborazinyl [(C2H5)3B3N3H2]2[C2H5]B3N3H3 (4) was prepared in analogous fashion. Poly(borazin-2-yl)amines containing borazine rings linked by nitrogen (5,6) have been obtained by the interaction of B-monohaloborazines with either HN[Si(CH3)3]2, N[Si(CH3)3]3, or N-lithioaminoborazines, but the reaction of NH3 with B-haloborazines containing annular NH groups preferentially leads to inseparable oligomer mixtures. The reaction of (methylthio)borane species such as B(SCH3)3, (CH3SBNCH3)3, or (CH3S)(C2H5)2B3N3H3 with aminoborazine derivatives generally also gives product mixtures in a series of sequential processes, although the 2,4-bis(borazin-2-ylamino)borazine (C-H3)3N3B3[C2H5][HN(C2H5)2B3N3(CH3)3]2 (8) was obtained from the reaction of (CH3S)2(C2H5)B3N3(CH3)3 with 2 molar equiv of (H2N)(C2H5)2B3N3(CH3)3. The 2,4,6-tris(borazin-2-ylamino)borazine [(CH3)3N3B3(CH3)2NH]3B3N3(CH3)3 (10b) was prepared by the reaction of (CIBNCH3)3 with 3 molar equiv of (LiHN)(CH3)2B3N3(CH3)3.