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.

The structures and the alkene dissociation energies of various metal–alkene complexes having the metal centers with different oxidation states and the alkene ligands with different substituents have been calculated. Correlations between the partial charges of the coordinated alkenes and the relative alkene dissociation energies were examined. The relative importance of σ donation and π back-donation in the metal–alkene interactions has been discussed.Figure optionsDownload as PowerPoint slide