An ab initio CI investigation of structure and bonding in LiC2H2 complexes
Résumé
The structures and energies of various LiC2H2 complexes have been investigated by means of ab initio molecular orbital calculations. Analytic SCF gradients were employed with a double-ζ basis set to locate and characterize stationary points on the energy surface. Single-point CI calculations using a double-ζ + diffuse and polarization basis set have been carried out at the DZ + P SCF stationary points. With the highest-level theory, the Li-vinylidene complex and the cis bridged adduct are found to be the most favorable arrangements, the former complex being slightly more stable by about 2 kcal mol-1. These molecules are bound respectively by about 5 and 3 kcal mole-1 relative to infinitely separated lithium plus acetylene. Harmonic vibrational frequencies are also reported and confirm the existence of the cis LiC2H2 species recently observed in a solid argon matrix. © 1987.