The structure and bonding of the AlC2H4 radical complex and its positive and negative ions have been characterized by ab initio molecular orbital methods. It is found that electron correlation is essential to the binding. A symmetric π-complex between Al atom and C2H4 is the global minimum for AlC2H4 with a binding enthalpy of 12 kcal/mol at the UMP4SDTQ/6-31 + G(d) level. The complexation energies for the ionic species are predicted to be 12.8 and 25.4 kcal/mol for C2H4Al+ and C2H4Al-, respectively. The trends in structural change mirror the correlation energy differences of the three systems. The computed CC bond lengthening of 0.07 Å for the 2B2 ground state of the AlC2H4 radical, relative to C2H4, is in accord with the estimated increase of 0.12 ± 0.02 Å based on the IR spectrum.
Bibliographical noteFunding Information:
This work wass upportedin part by the National ScienceF oundation.C omputationaal ssistanfcreo m Dr. A.D. MacKerelIi s gratefullya cknowledgedTh. e computationswerdeo nea tCray ResearchW. e thank Dr. Eric Wimmer for makingt his possible.
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