The LiC2H2and NaC2H2adducts

Autor: Minh Tho Nguyen, M. Yoshimine, Tae-Kyu Ha
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