Ab initio analysis of pentadienyllithium, pentadienylsodium, and the pentadienyl ions

Ab initio calculations were used to determine the equilibrium geometries and rotational barriers of the pentadienyl cation, anion, and metalated pentadienes. Pentadienyllithium and pentadienylsodium are most stable in a U-shaped structure. This geometry is a higher energy local minimum for the pentadienyl anion and is not a stationary point for the pentadienyl cation. The atomic and group charges were analyzed by natural population analysis and were determined for each of the conformations studied.