The LiC2H2and NaC2H2adducts
Autor: | Minh Tho Nguyen, M. Yoshimine, Tae-Kyu Ha |
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Rok vydání: | 1992 |
Předmět: | |
Zdroj: | Molecular Physics. 77:921-936 |
ISSN: | 1362-3028 0026-8976 |
DOI: | 10.1080/00268979200102871 |
Popis: | Ab initio molecular orbital calculations were employed to re-examine a number of structural and energetic aspects of both LiC2H2 and NaC2H2 adducts. Geometries were optimized using UMP2/6-311++G(d,p) wave-functions, while relative energies were uniformly estimated at the PUMP4/6-311++G(d,p)+ZPE level. The QCISD(T) method and 6-311++G(2df,2pd) basis set were also considered. Each metal-acetylene has a cis-bent bridged geometry and a 2B2 ground electronic state. The 2A′ and 2A1 forms exist as shallow minima only for lithium-acetylene. Metal-acetylenes have 2B2 ground states. In each system, both isomers have similar energies and are separated from each other by a substantial energy barrier. While lithium-acetylene is observable, sodium-acetylene is not stable with respect to fragmentation. Conversion of sodium plus acetylene to sodium-vinylidene, without initial formation of a sodium-acetylene intermediate, is shown to be possible through a ‘neutral pathway’. This process is, however, endothermic, not spont... |
Databáze: | OpenAIRE |
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