MODELS AND POLYBORAZINE PRECURSORS FOR BORON-NITRIDE CERAMICS

Elimination-condensation reactions between Me(Cl2)B3N3Me3 and (Me3Si)2NMe and between (ClBNMe)3 and (Me3Si)2NH form oligomeric borazinylamines, and a metathesis reaction between Li2S and (ClBNH)3 produces an oligomeric borazinyl sulfide. The pyrolysis chemistry of these oligomers has been examined, and conditions have been defined that produce hexagonal h-BN. Reactions that model the first stage of oligomer formation also have been studied, and the molecular species [Me3N3B3(Me2)]2NH, [Me3N3B3- (Me2)]2NMe, [Me3N3B3(Me2)]2S, and [Me3N3B3(Me2)]2O have been isolated and characterized. Single-crystal X-ray diffraction analyses for these compounds have been completed, and crystal data are as follows: [Me3N3B3(Me2)]2NH, triclinic, [formula omitted], Z = 2, at 293 K, a = 8.078 (1) Å, b = 9.121 (1) Å, c = 14.139 (2) Å, α= 97.07 (1)°, β = 95.44 (1)°, γ = 115.32 (1)°, and V = 921.8 (2) Å3; [Me3N3B3(Me2)]2NMe, triclinic, [formula omitted], Z = 2, at 293 K, a = 8.075 (2) Å, b = 9.210 (2) Å, c = 14.912 (3) Å, α = 91.51 (2)°, β = 94.07 (2)°, γ = 113.27 (2)°, and V = 1007.0 (5) Å3; [Me3N3B3(Me2)]2O, orthorhombic, Pbcn, Z = 4, at 293 K, a = 14.166 (7) Å, b = 11.378 (6) Å, c = 11.983 (6) A, and V = 1931 (2) Å3; [Me3N3B3(Me2)]2S, monoclinic P2/n, Z = 2, at 293 K, a = 6.339 (1) Å, b = 6.351 (1) Å, c = 23.677 (4) Å, β = 97.42 (1)°, and V = 945.3 (2) Å3. The molecular structure of each compound features a central atom, N(H), N(Me), O, or S, bonded to two pentamethylborazinyl rings. © 1990, American Chemical Society. All rights reserved.