Synthesis and X-ray crystallographic studies of diacetylenic molecules bearing triorganosilyl, triorganostannyl, and diorganophosphanyl substituents.: Investigation of their solid-state and molten-state polymerization

The following series of silicon-containing diacetylenes has been prepared: R(3)SiCequivalent toCCequivalent to CSiR3 (R-3 = Me-3 (2a); R-3 = Me2Ph (2b); R-3 = MePh2 (2c); R-3 = Ph-3 (2d)), rac-MePhNpSiCequivalent toCCequivalent toCSiMePhNp (2e: Np = 1-naphthyl), (R,R)-(+)-MePhNpSiCequivalent toCCequivalent toCSiMePhNp (2e*), rac-Ph(3)SiCequivalent toCCequivalent toCSiMePhNp (3), (R)-(+)-Ph(3)SiCequivalent toCCequivalent toCSiMePhNp (3*), R(3)SiCH(2)Cequivalent toCCequivalent to CCH2SiR3 (R-3 = Me-3 (4a); R-3 = Ph-3 (4b)), R(2)HSiCequivalent toCCequivalent toCSiHR(2) (R-2 = Me-2 (5a); R-2 = Ph-2 (5b)), R(3)SiCequivalent toCCequivalent toCH (R-3 = Me-3 (6a); R-3 = Ph-3 (6b)), and rac-MePhNpSiCequivalent toCCequivalent toCH (6c). Single-crystal X-ray diffraction analyses were performed on 2a, 2d, 2e*, 4a, and 4b to determine the R-1,R-4 distance and the angle gamma between neighboring diacetylenic rods in the solid. Diacetylenes 2a, 2e*, and 4a were tested for gamma-ray and heat-induced solid-state polymerization reactivity, and in accordance with the X-ray results, polymerization was not observed. Terminal diyne 6c showed no polymerization activity upon irradiation with a 100 krad dose of gamma-rays but slowly polymerized in the solid state when heated to 70 degreesC for 13 days. Following a preliminary investigation of 2a, 2d, 2e, 2e*, 3*, 4a, 4b, 5a, 5b, 6a, 6b, and 6c by differential scanning calorimetry (DSC), these diynes were polymerized in the molten state or just below melting. MALDI-TOF mass spectrometry shows that the polymers consist of mixtures of oligomers with 2 to 10 repeat units. The constituting motif of these oligomers (enyne, butatriene, polyaromatic) was elucidated by use of infrared and solution and solid-state multinuclear NMR spectroscopies. Polymerization experiments were also carried out on Me(3)SnCequivalent toCCequivalent toCSnMe(3) (7a), Ph(3)SnCequivalent toCCequivalent toCSnPh(3) (7b), and Ph(2)PCequivalent toCCequivalent toCPPh(2) (8), and the results of these experiments are compared with the polymerization results of their silicon-containing analogues. A 1,4-addition process takes place with 2a, 2d, 2e, 2e*, 3*, 5a, 5b, 7a, 7b, and 8, leading to butatriene and/or enyne structures. A 1,2-addition process is operative in the case of monosilylated derivatives 6a, 6b, and 6c, giving acetylenic polyenes. Molten-state polymerization of 4a and 4b gives polyaromatic structures.