Synthesis and X-ray Crystallographic Studies of Diacetylenic Molecules Bearing Triorganosilyl, Triorganostannyl, and Diorganophosphanyl Substituents. Investigation of Their Solid-State and Molten-State Polymerization

Abstract

The following series of silicon-containing diacetylenes has been prepared: R3SiC⋮CC⋮CSiR3 (R3 = Me3 (2a); R3 = Me2Ph (2b); R3 = MePh2 (2c); R3 = Ph3 (2d)), rac-MePhNpSiC⋮CC⋮CSiMePhNp (2e: Np = 1-naphthyl), (R,R)-(+)-MePhNpSiC⋮CC⋮CSiMePhNp (2e*), rac-Ph3SiC⋮CC⋮CSiMePhNp (3), (R)-(+)-Ph3SiC⋮CC⋮CSiMePhNp (3*), R3SiCH2C⋮CC⋮CCH2SiR3 (R3 = Me3 (4a); R3 = Ph3 (4b)), R2HSiC⋮CC⋮CSiHR2 (R2 = Me2 (5a); R2 = Ph2 (5b)), R3SiC⋮CC⋮CH (R3 = Me3 (6a); R3 = Ph3 (6b)), and rac-MePhNpSiC⋮CC⋮CH (6c). Single-crystal X-ray diffraction analyses were performed on 2a, 2d, 2e*, 4a, and 4b to determine the R 1,4 distance and the angle γ between neighboring diacetylenic rods in the solid. Diacetylenes 2a, 2e*, and 4a were tested for γ-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 γ-rays but slowly polymerized in the solid state when heated to 70 °C 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 Me3SnC⋮CC⋮CSnMe3 (7a), Ph3SnC⋮CC⋮CSnPh3 (7b), and Ph2PC⋮CC⋮CPPh2 (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.

Tris(biphenyl‐4‐yl)silyl‐Endcapped Polyynes

“…[2] This sterically demanding endgroup places each polyyne a distance of Ͼ 8 Å from its nearest neighbor in the crystal lattice, double of that required for an intermolecular reaction to occur (Figure 2, b). [8,13] Diyne 3 shows a melting point (296-298°C) that is comparable to 1,4-bis(triphenylsilyl)-1,3-butadiyne (304°C) [14] and higher than that of 1,4-bis(methyldiphenylsilyl)-1,3-butadiyne (143°C). [13] These values are higher than those of trialkylsilyl-endcapped diynes such as 1,4-bis(TIPS)-1,3-butadiyne (98-100°C) [2] and 1,4-bis(TMS)-1,3-butadiyne (107°C).…”

“…[8,13] Diyne 3 shows a melting point (296-298°C) that is comparable to 1,4-bis(triphenylsilyl)-1,3-butadiyne (304°C) [14] and higher than that of 1,4-bis(methyldiphenylsilyl)-1,3-butadiyne (143°C). [13] These values are higher than those of trialkylsilyl-endcapped diynes such as 1,4-bis(TIPS)-1,3-butadiyne (98-100°C) [2] and 1,4-bis(TMS)-1,3-butadiyne (107°C). [15] This suggests a possible trend in melting point related to structure of the terminal silyl group (i.e., aryl vs. alkyl substituents), rather than overall size.…”

Diacetylenes with Ionic‐Liquid‐Like Substituents: Associating a Polymerizing Cation with a Polymerizing Anion in a Single Precursor for the Synthesis of N‐Doped Carbon Materials

“…As imilar polymerization process has been shown to occur during molten-state polymerization of disilylatedd iynes R 3 SiCCCCSiR 3 ,a lthough in this case concomitant formation of polymers with butatriene structures was observed. [22] Polymers with structural arrangements other than enyne and/or butatriene forms have been found to result from thermal polymerization of HCCCCH deposited onto an organic polymer substrate surface and from molten-state polymerization of PhCCCCPh. [23] The proposed polymerics tructures include polyenes with acetylenic dangling groups, polyacenes, and polyphenyl structures with acetylenic substituents.L astly,w ork has also been published in which the structure of the polymeric substance resulting from the exothermic process could not be elucidated because of the intractable nature of the residue and/or the presence of carbon-centered radicals.…”

“…In fact, detection in the solid-state 13 CNMR spectra of both pyrolysates of large signals centered at 130 ppm underneath the signals due to the imidazolium and benzimidazoliums ubstituents is consistent with the presence of polyaromatic structures. [19,22] The N1sX Ps pectrao ft he formed polymers should be the same as those of the precursors. However, comparison of the N1 sX Ps pectra of the bromide precursors with those of the compounds thermolyzed at 220 8Cr eveals some differences ( Figure 7).…”

Organodilithium Intermediates as Useful Dianionic Synthons: Recent Advances

“…Enantiomerically enriched (R)-2,2'-dilithio-1,1'-binaphthyl (110) was also prepared by bromine-lithium exchange with n-BuLi at low temperature from the corresponding dibromide 109. The reaction of the intermediate 110 with trialkylhalosilanes gave 2,2'-bis-silyl-substituted 1,1'-binaphthyls 111 (Scheme 27) [60].…”