In-depth insight into metal-alkene bonding interactions

The relative alkene dissociation energies and the structures of Pd(PH₃)₂(η²-CH₂CHX), trans-[Pd(PH₃)₂Cl(η²-CH₂CHX)]⁺, trans-[Pd(PH₃)Cl₂(η²-CH₂CHX)], Cp₂Zr(PH₃)(η²-CH₂CHX) and [Cp₂Zr(CH₃)(η²-CH₂CHX)]⁺ (X = CN, Cl, Br, Me, OMe, NMe₂) were calculated with the B3LYP density functional theory. We examined the correlations between the partial charges of the coordinated alkenes and the relative alkene dissociation energies. Through these correlations, we have been able to see how the alkene(π)-to-metal(d) donation and metal(d)-to-alkene(π*) back-donation interactions affect the relative alkene dissociation energies. We also examined the calculated structures and found that the Zr(IV) and Pd(II) complexes have a rather asymmetric alkene coordination while the Zr(II) and Pd(0) complexes have an approximately symmetric alkene coordination. The effects of the alkene(π)-to-metal(d) donation and metal(d)-to-alkene(π*) back-donation interactions on the structural features have also been discussed.