Conformational analysis of a TADDOL-based phosphoramidite P,N ligand in a palladium(II) η3-π-allyl complex
| Autor: | Abdurrahman C. Atesin, Oscar P. Rodriguez, Tülay A. Ateşin, Lohany Y. Garcia, Diego Rivera |
|---|---|
| Rok vydání: | 2018 |
| Předmět: |
Phosphoramidite
010405 organic chemistry Ligand chemistry.chemical_element 010402 general chemistry Condensed Matter Physics Ring (chemistry) 01 natural sciences Biochemistry 0104 chemical sciences Bond length Crystallography Tsuji–Trost reaction chemistry Intramolecular force Physical and Theoretical Chemistry Conformational isomerism Palladium |
| Zdroj: | Computational and Theoretical Chemistry. 1139:70-76 |
| ISSN: | 2210-271X |
| DOI: | 10.1016/j.comptc.2018.07.007 |
| Popis: | The most stable conformations of a TADDOL-based phosphoramidite P,N ligand coordinated to a palladium(II) η3-π-allyl fragment have been investigated using molecular mechanical and quantum mechanical calculations. The conformational analysis initially generated 53 unique structures within 5 kcal/mol and subsequent geometry optimization narrowed the number of low-energy conformers down to 13. The two lowest energy conformers differ mainly in the conformation of the allyl group. The conformer with an endo allyl group has a slightly higher relative energy than the conformer with an exo allyl group. Comparison of the main geometric parameters around the Pd(II) metal center in the two lowest energy conformers with the available X-ray single crystal structures of Pd(II) η3-π-allyl complexes of P,N ligands shows a good agreement in both the bond lengths and angles. The lowest energy structure has a “chair” conformation of the seven-membered phospha-dioxa-cycloheptane ring and “edge-on/face-on/face-on/edge-on” arrangement of the phenyl rings. The next lowest energy conformer with an exo allyl group has a “twist” conformation of the seven-membered ring and alternating “edge-on” and “face-on” arrangement of the phenyl rings as anticipated from the Knowles “edge-on/face-on” concept. The results of this study support published hypotheses regarding the origin of the chiral induction in the enantioselective Pd(0) catalyzed intramolecular allylic alkylation reaction by the repulsive interactions between one of the phenyl groups in the seven-membered ring in the lowest energy conformer of the ligand with the substrate. As such, the results of this research can be used to guide the synthesis of new and improved variants of this important catalyst family. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|
Full Text from ScienceDirect