Bonding, Electronic, and Vibrational Analysis of the Al−C2H4 Complex Using Density Functional Theory and Topological Method (ELF)

The density functional theory (DFT) has been used to reexamine the Al−C2H4 complex because of discrepancies between the results of post-Hartree−Fock methods concerning the binding energy and the ordering of the metal−ligand stretching frequencies. In this study, equilibrium geometry, binding energy, and harmonic frequencies have been calculated using the 6-311G(2d,2p) basis set. It is shown that the Al−C2H4 complex has a C2v symmetry equilibrium structure and a 2B2 ground electronic state, which is strongly bound by −13.3 kcal/mol after BSSE correction (to be compared to the −16 kcal/mol experimental value). The bonding in the Al−C2H4 complex has been investigated by the electron localization function (ELF). The aluminum−ethylene bonding is found to be mostly electrostatic. The degree of weakening of the CC double bond and the ordering of the two metal−carbon stretching modes have been discussed using a harmonic vibrational and force constant analysis and compared to the experimental results. Furthermore,...