Dehydrocoupling of tris(hydridosilylethyl)boranes with ammonia or amines: a novel route to Si–B–C–N preceramic polymers

The synthesis of boron‐modified polysilazanes­of general type {B[C 2 H 4 Si(R)NR′] 3 } n [R = CH 3 , (NR′) 0.5 ; R′ = H, CH 3 ] by dehydrogenative coupling of tris(hydridosilylethyl)boranes B[C 2 H 4 Si(CH 3 ) n H 3− n ] 3 (C 2 H 4 = CHCH 3 , CH 2 CH 2 ; n = 0, 1) and ammonia or methylamine is reported. Detailed characterization of the title compounds was performed using spectroscopic methods such as solid‐state NMR spectroscopy, IR spectroscopy, and elemental analysis. Thermolysis produces amorphous Si–B–C–N ceramics with ceramic yields between 25 and 83%, as determined by thermogravimetric analysis (TGA) in argon. High‐temperature TGA in an argon atmosphere reveals that a number of the ceramics obtained resist degradation up to ∼2000 °C. X‐ray diffraction studies of the as‐obtained amorphous materials show formation of α‐SiC or α‐SiC/β‐Si 3 N 4 crystalline phases between 1600 and 1800 °C, depending on the composition of the materials.