Thermal isomerization and decomposition of ethynyldisilanes
Co-pyrolysis of ethynylpentamethyldisilane with 2,3-dimethylbutadiene afforded trimethylsilylacetylene, dimethylsilyl(trimethylsilyl)acetylene and 1,1,3,4-tetramethyl-1-silacyclopent-3-ene. When an alkyl or trimethylsilyl substituted ethynyl group was pyrolyzed, extrusion of dimethylsilylene was the only decomposition process observed with no isomerization. The decomposition and isomerization pathways and Arrhenius parameters were determined for these processes by using a pulse stirred-flow reactor. Pyrolysis of ethynylundecamethylcyclohexasilane afforded the ring-expanded isomer 3 hydridoundecainetliylliexasilacyclooctyne and decamethylpentasilacycloheptyne. Pyrolysis of 4.4,5,5,6,6,7,7,8,8-decamethyl-4,5,6,7,8-pentasilacyclooctyne afforded ring-contracted isomer 1,1-penta(dimethylsilylene)propadiene, 4,4,5,5,6,6,7,7-octamethyl4,5,6,7-tetrasilacycloheptyne, 1, and 1,1-tetra(dimethylsilylene)propadiene, 2. Cycloheptyne 1 was also pyrolyzed and afforded propadiene 2 as the only product. Several mechanisms were proposed for these decompositions and isomerizations. Bis[1,3-tetra(dimethylsilylene)]propadiene, 3, was synthesized from cycloheptyne 1 in 20% yield. An x-ray structure of the smallest ``betweenallene``, 3, was determined. Pyrolysis of propadiene 3 afforded isomer 1,1-3,3-bis[tetra(dimethylsilylene)]propadiene as the only observed product. The proposed mechanism involved cyclopropene intermediates.
- Research Organization:
- Ames Lab., IA (United States)
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- W-7405-ENG-82
- OSTI ID:
- 10178662
- Report Number(s):
- IS-T-1351; ON: DE92040578
- Resource Relation:
- Other Information: TH: Thesis (Ph.D.); PBD: Jul 1992
- Country of Publication:
- United States
- Language:
- English
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