A systematic examination of ligand basicity effects on bonding in palladium(0)- and palladium(II)-ethylene complexes
| Autor: | John T. York, Jacob B. Geri |
|---|---|
| Rok vydání: | 2018 |
| Předmět: |
chemistry.chemical_classification
Ethylene 010405 organic chemistry Ligand Alkene chemistry.chemical_element Interaction energy 010402 general chemistry 01 natural sciences 0104 chemical sciences Inorganic Chemistry Bond length chemistry.chemical_compound Crystallography chemistry Materials Chemistry Molecular orbital Physical and Theoretical Chemistry Natural bond orbital Palladium |
| Zdroj: | Inorganica Chimica Acta. 483:191-202 |
| ISSN: | 0020-1693 |
| Popis: | The impact of ancillary ligand basicity on the binding and activation of ethylene in a series of [(L)Pd0(C2H4)] and [(L)PdII(C2H4)]2+ complexes (where L = substituted 1,10-phenanthroline ligands) has been studied with density functional theory using natural bond orbital (NBO) analysis, energy decomposition analysis (EDA-NOCV), and molecular orbital (MO) analysis. With palladium(0), metrics of ethylene C C bond activation are strongly correlated with increasing ligand basicity, including the C C bond length and vibrational frequency, the magnitude of Pd(0) → ethylene(π∗) NBO donation, and the Wiberg C C bond index. In contrast, ethylene(π) → Pd(0) donation is not strongly influenced by ligand basicity, which is manifested in strong correlations between Pd(0) → ethylene(π∗) donation and both C C bond length and ν(CC). EDA-NOCV results show that the [(L)Pd0]-(C2H4) interaction energy is dominated by Coulombic attraction and enhanced slightly with more electron-donating ligands. MO analysis demonstrates that a linear increase in the energy of the filled [(L)Pd0] HOMO with ligand pKa is directly correlated with the enhanced [(L)Pd0] → ethylene(π∗) donation. For the [(L)PdII(C2H4)]2+ adducts, C C bond lengthening and weakening is roughly half the amount observed with Pd0, with ligand substitution having a negligible impact. NBO analysis confirms that ethylene activation is dominated by ethylene(π) → PdII donation, which is enhanced with electron-withdrawing ligands while PdII → ethylene(π∗) donation decreases with less basic ligands. EDA-NOCV results show that the [(L)PdII]2+-(C2H4) interaction energy is also dominated by Coulombic attraction and is enhanced by more electron-withdrawing ligands, largely as a result of a concurrent increase in ethylene(π) → [(L)PdII]2+ stabilization and a decrease in Pauli repulsion. Finally, MO analysis indicates an electrophilic ethylene moiety due to substantial stabilization of both the alkene π- and π∗-orbitals through interaction with the [(L)PdII]2+ fragment. |
| Databáze: | OpenAIRE |
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