Ion pairing effects in intramolecular heterolytic H2 activation in an Ir(iii) complex: a combined theoretical/experimental study
| Autor: | Karin Gruet, Ben P. Patel, Alceo Macchioni, Odile Eisenstein, Robert H. Crabtree, Dong Heon Lee, Eric Clot |
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| Přispěvatelé: | Department of Chemistry [New Haven], Yale University [New Haven], Laboratoire de structure et de dynamique des systèmes moléculaires et solides (LSDSMS), Université Montpellier 2 - Sciences et Techniques (UM2)-Centre National de la Recherche Scientifique (CNRS), Department of Chemistry, Chonbuk National University, Dipartimento di Chimica, Università degli Studi di Perugia (UNIPG) |
| Rok vydání: | 2002 |
| Předmět: |
ONIOM
Steric effects CATALYSTS 010402 general chemistry Photochemistry 01 natural sciences Heterolysis Catalysis Dissociation (chemistry) Ion CHEMISTRY ANION Materials Chemistry Electronic effect HYDROGENATION OLEFIN COORDINATION DIOLEFIN COMPLEXES 010405 organic chemistry Hydride Chemistry General Chemistry 0104 chemical sciences Crystallography Intramolecular force [PHYS.PHYS.PHYS-CHEM-PH]Physics [physics]/Physics [physics]/Chemical Physics [physics.chem-ph] DIHYDROGEN IRIDIUM |
| Zdroj: | New Journal of Chemistry New Journal of Chemistry, Royal Society of Chemistry, 2003, 27, pp.80-87. ⟨10.1039/b207339k⟩ |
| ISSN: | 1369-9261 1144-0546 |
| DOI: | 10.1039/b207339k |
| Popis: | International audience; A free pendant 2-amino group in a benzoquinolinate ligand bound to Ir(III) can cause heterolytic dissociation of an adjacent Ir-H-2, depending on the nature of the phosphine, L. For L=PMePh2, heterolysis does not occur and an H-2 complex, [IrH(H-2)(bq-NH2)L-2]BF4, is seen, but if L=PPh3 or PCy3, heterolysis does occur and a hydride product, [IrH2(bq-NH3)L-2]BF4, is formed by proton transfer from the bound H-2 to the pendant NH2 group. The electronic effect of L is not dominant. Theoretical studies (DFT calculations) show that the H-2 complex is predicted to be more stable for all the phosphines used, if the anion is ignored. We propose that the hydride isomer, formed when L is bulky, depends on ion pairing effects for its stability. The calculated electrostatic potentials for the two isomers suggest that the counter anion has to be located much closer to the metal in the H-2 complex than in the hydride where the anion is much farther from the metal. The bulky phosphines PPh3 and PCy3 favor remote ion pairing and therefore favor the hydride isomer because steric effects disfavor close ion pairing as confirmed by ONIOM (B3PW91/UFF) calculations of the ion pair geometry. An improved synthesis of [IrH5(PCy3)(2)] is reported. |
| Databáze: | OpenAIRE |
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