Theoretical studies of organometallic compounds. 60: Ethylene addition to group-9 transition metal dioxo compounds - A quantum chemical study

Quantum chemical calculations employing density functional theory (B3LYP) have been carried out to elucidate the reaction pathways for ethylene addition to iridium [IrO₂CH₃CH₂], rhodium [RhO ₂CH₃CH₂] and cobalt [CoO₂CH ₃CH₂] complexes. The comparison of the results shows that all three complexes prefer a [3+2] cycloaddition pathway rather than a [2+2] addition. For the iridium and rhodium species, the [3+2]_C,O pathway where the transition metal-carbon and transition metal-oxygen double bonds are involved is favoured, whereas the cobalt compound prefers the [3+2] _O,O addition where both transition metal-oxygen double bonds are participating with concomitant hydrogen migration. For all three metal compounds, the reaction energies are highly exothermic and only small barriers are necessary to overcome.