The pyrolysis of 2C=CC=C-]" under a stream of argon to 1400 °C gives a /3-SiC-containing ceramic in high yield (84%). The polymer-to-ceramic conversion chemistry was studied by means of thermal analysis, infrared spectroscopy, solid-state 13C NMR spectroscopy, and X-ray powder diffraction. Gaseous products were analyzed by mass spectrometry. The polymer primarily undergoes low-temperature cross-linking through the diacetylene groups at about 200 °C, i.e., 300 °C below the mineralization stage. Decomposition reactions occur between 450 and 800 °C inside a highly cross-linked carbon network. The weight decrease arises only from loss of CH4 and H2. The total amount of silicon remains in the final residue. From a mechanistic point of view, [-Si(CH3)2C^CC^C-]" is of interest as a suitable model to explore the mechanism of the thermal conversion of silicon-containing polymers into silicon carbide. The formation of SiC takes place inside an amorphous carbon matrix and only involves silyl units that contain no Si-H or functional groups and that are separated from one another. Some implications are discussed. Pyrolysis under ammonia leads to Si3N4 with loss of carbon and evolution of HCN.

The reaction of dilithiobutadiyne (or the corresponding di-Grignard reagent) with various dichlorosilanes and dibromogermanes in THF at room temperature afforded poly[(silylene)diacetylenes] and poly[(germylene)diacetylenes], respectively, in high yields. The polymers have a regular alternating arrangement of diyne and silylene or germylene units. When they are doped with FeCl3, these polymers show conductivity values in the range 10r5-10r3 S-cm'1. The values depend greatly on the electronic character of the substituents bonded to silicon or germanium.

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