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García-Iglesias M, Buñuel E, Cárdenas DJ. Cationic (η1-Allyl)-palladium Complexes as Feasible Intermediates in Catalyzed Reactions. Organometallics 2006. [DOI: 10.1021/om060199+] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Cárdenas DJ, Martín-Matute B, Echavarren AM. Aryl Transfer between Pd(II) Centers or Pd(IV) Intermediates in Pd-Catalyzed Domino Reactions. J Am Chem Soc 2006; 128:5033-40. [PMID: 16608337 DOI: 10.1021/ja056661j] [Citation(s) in RCA: 159] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A computational study has been performed to determine the mechanism of the key steps of Pd-catalyzed domino reactions in which C(sp2)-C(sp2) are formed from aryl and alkenyl halides. DFT calculations were done on model complexes of the proposed intermediates, with PH3 and H2O as ancillary ligands, to explore two possible mechanisms: the oxidative addition of aryl or alkenyl halides to palladacycles to give Pd(IV) intermediates, and the transmetalation-type reaction of aryl or alkenyl ligands between two Pd(II) centers, a palladacycle, and a Pd(II) complex formed by oxidative addition of aryl or alkenyl halides to Pd0. We have shown that oxidative addition of iodoethylene to Pd0 precursors is more favorable than oxidative addition to Pd(II) palladacycles, whereas transmetalation-type reactions between Pd(II) complexes are facile. Similar results were obtained with iodobenzene instead of iodoethylene and formamide as the ancillary ligand. These results suggest that Pd(IV) intermediates are not involved in these reactions.
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Affiliation(s)
- Diego J Cárdenas
- Departamento de Química Organica, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain.
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Prager M, Grimm H, Natkaniec I. Rotational tunneling of methyl groups in low temperature phases of mesitylene: potentials and structural implications. Phys Chem Chem Phys 2005; 7:2587-93. [PMID: 16189568 DOI: 10.1039/b503342j] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Mesitylene can be stabilized at He temperature in three solid phases of so far unknown crystal structures. Rotational tunneling of methyl groups is based on rotational potentials and used to characterize structural aspects. In phase III found after the first fast cooling of the sample three nonequivalent methyl rotors with splittings of 2.7, 4.1 and 16.3 microeV are observed. Three other unresolved bands are identified by their librational modes. In the second phase II the metastability is emphasized by tunneling energies still changing at temperatures T< or = 12 K. Above this temperature tunneling bands at 6.6, 12.5, 15.0 and 18.3 microeV evolve in the manner characteristic of coupling to phonons. In the equilibrium phase I a single tunnel splitting of 10.2 microeV represents all methyl groups. A unit cell containing a single molecule at a site of threefold symmetry explains quantitatively this spectrum. Phases II and III most likely contain two nonequivalent molecules in the unit cell with no local symmetry in phase II and a mirror plane in phase III. The good moderator properties for neutrons are most likely not connected to the low energy tunneling bands but to a dense vibrational phonon density of states.
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Affiliation(s)
- M Prager
- Institut für Festkörperforschung, Forschungzzentrum Jülich, D-52425 Jülich, Germany
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Nair S, Dimeo RM, Neumann DA, Horsewill AJ, Tsapatsis M. Methyl rotational tunneling dynamics of p-xylene confined in a crystalline zeolite host. J Chem Phys 2004; 121:4810-9. [PMID: 15332915 DOI: 10.1063/1.1781119] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The methyl rotational tunneling spectrum of p-xylene confined in nanoporous zeolite crystals has been measured by inelastic neutron scattering (INS) and proton nuclear magnetic resonance (NMR), and analyzed to extract the rotational potential energy surfaces characteristic of the methyl groups in the host-guest complex. The number and relative intensities of the tunneling peaks observed by INS indicate the presence of methyl-methyl coupling interactions in addition to the methyl-zeolite interactions. The INS tunneling spectra from the crystals (space group P2(1)2(1)2(1) with four crystallographically inequivalent methyl rotors) are quantitatively interpreted as a combination of transitions involving two coupled methyl rotors as well as a transition involving single-particle tunneling of a third inequivalent rotor, in a manner consistent with the observed tunneling energies and relative intensities. Together, the crystal structure and the absence of additional peaks in the INS spectra suggest that the tunneling of the fourth inequivalent rotor is strongly hindered and inaccessible to INS measurements. This is verified by proton NMR measurements of the spin-lattice relaxation time which reveal the tunneling characteristics of the fourth inequivalent rotor.
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Affiliation(s)
- Sankar Nair
- School of Chemical & Biomolecular Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0100, USA.
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Boudjada A, Meinnel JJ, Boucekkine A, Hernandez OJ, Fernández-Diaz MT. Molecular conformation and methyl proton delocalization in triiodomesitylene: A combined density functional theory and single-crystal neutron diffraction study. J Chem Phys 2002. [DOI: 10.1063/1.1519535] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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Kirstein O, Prager M, Johnson MR, Parker SF. Lattice dynamics and methyl rotational excitations of 2-butyne. J Chem Phys 2002. [DOI: 10.1063/1.1485729] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Moreno AJ, Alegrı́a A, Colmenero J, Prager M, Grimm H, Frick B. Methyl group dynamics in glassy toluene: A neutron scattering study. J Chem Phys 2001. [DOI: 10.1063/1.1413742] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Sundermann A, Uzan O, Martin JML. Exclusive C−C Activation in the Rhodium(I) PCN Pincer Complex. A Computational Study. Organometallics 2001. [DOI: 10.1021/om0100838] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Andreas Sundermann
- Department of Organic Chemistry, Kimmelman Building, Room 262, Weizmann Institute of Science, IL-76100 Rechovot, Israel
| | - Olivier Uzan
- Department of Organic Chemistry, Kimmelman Building, Room 262, Weizmann Institute of Science, IL-76100 Rechovot, Israel
| | - Jan M. L. Martin
- Department of Organic Chemistry, Kimmelman Building, Room 262, Weizmann Institute of Science, IL-76100 Rechovot, Israel
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Johnson MR, Kearley GJ. Quantitative atom-atom potentials from rotational tunneling: their extraction and their use. Annu Rev Phys Chem 2000; 51:297-321. [PMID: 11031284 DOI: 10.1146/annurev.physchem.51.1.297] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Rotational tunneling of small molecular groups has been the subject of considerable theoretical and experimental activity for several decades. Much of this activity has been driven by the promise of exploiting the extreme sensitivity of quantum tunneling to interatomic potentials, but until recently, there was no straightforward means by which quantitative information about these potentials could be extracted. This review explains how a quantitative method, suitable for general application, was developed. It then goes on to show how this has been used to understand tunneling systems for which no previous satisfactory explanation had been found. The application of the methodology, and its results, to other disciplines is discussed.
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Affiliation(s)
- M R Johnson
- Institut Laue Langevin, BP 156, 38042 Grenoble, Cedex 09, France.
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11
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Sundermann A, Uzan O, Milstein D, Martin JML. Selective C−C vs C−H Bond Activation by Rhodium(I) PCP Pincer Complexes. A Computational Study. J Am Chem Soc 2000. [DOI: 10.1021/ja000943w] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Andreas Sundermann
- Contribution from the Department of Organic Chemistry, Weizmann Institute of Science, Kimmelman Building, Room 262, IL-76100 Rehovot, Israel
| | - Olivier Uzan
- Contribution from the Department of Organic Chemistry, Weizmann Institute of Science, Kimmelman Building, Room 262, IL-76100 Rehovot, Israel
| | - David Milstein
- Contribution from the Department of Organic Chemistry, Weizmann Institute of Science, Kimmelman Building, Room 262, IL-76100 Rehovot, Israel
| | - Jan M. L. Martin
- Contribution from the Department of Organic Chemistry, Weizmann Institute of Science, Kimmelman Building, Room 262, IL-76100 Rehovot, Israel
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Pejov L, Ristova M, Zdravkovski Z, Šoptrajanov B. Ab initio quantum chemical and experimental study of structure, harmonic vibrational frequencies and internal Ph–SO 3 torsion of benzenesulfonate anion. J Mol Struct 2000. [DOI: 10.1016/s0022-2860(99)00455-x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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Ibberson R, David W, Parsons S, Prager M, Shankland K. The crystal structures of m -xylene and p -xylene, C 8 D 10 , at 4.5 K. J Mol Struct 2000. [DOI: 10.1016/s0022-2860(99)00448-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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Sundermann A, Schoeller WW. Phosphorane−Iminato Complexes of Transition Metals with Heterocubane Structure: A Computational Study. J Am Chem Soc 2000. [DOI: 10.1021/ja992850o] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Ibberson R, Yamamuro O, Matsuo T. Crystal structures and phase behaviour of acetaldehyde-d4: a study by high-resolution neutron powder diffraction and calorimetry. J Mol Struct 2000. [DOI: 10.1016/s0022-2860(99)00337-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Sundermann A, Schoeller WW. Electronic Structure of Metallacyclophosphazene and Metallacyclothiazene Complexes. Inorg Chem 1999; 38:6261-6270. [PMID: 11671342 DOI: 10.1021/ic990956e] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The electronic structure of metallacyclotriphosphazene complexes with several substituents at the phosphorus atoms and metallacyclothiazene complexes is explored for a variety of transition metal elements using density functional theory methods. Accordingly the metallacyclophosphazenes possess a large HOMO-LUMO energy separation while the metallacyclothiazenes bear stronger open-shell character. In addition our calculations predict the existence of experimentally so far unknown dimetallacyclophosphazenes. All structures show to be highly dynamical. The double bond character of the transition metal nitrogen bond is much less pronounced than in nitrido or imido complexes. For the ring compounds vibrational spectra are reported and compared with experimental data.
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Affiliation(s)
- Andreas Sundermann
- Fakultät für Chemie, Universität Bielefeld, Postfach 100131, 33501 Bielefeld, Germany
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Johnson M, Prager M, Grimm H, Neumann M, Kearley G, Wilson C. Methyl group dynamics in paracetamol and acetanilide: probing the static properties of intermolecular hydrogen bonds formed by peptide groups. Chem Phys 1999. [DOI: 10.1016/s0301-0104(99)00138-x] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Prager M, Heidemann A. Rotational Tunneling and Neutron Spectroscopy: A Compilation. Chem Rev 1997; 97:2933-2966. [PMID: 11851482 DOI: 10.1021/cr9500848] [Citation(s) in RCA: 209] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- M. Prager
- Institut Laue-Langevin, B.P. 156, F-38042 Grenoble, France
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Mellor WE, Lee AR, Kalotas TM. A Systematic Approach for Determining Internal Rotation Potentials of Single-Top Molecules from Observed Transition Spectra. JOURNAL OF MOLECULAR SPECTROSCOPY 1997; 186:189-192. [PMID: 9417963 DOI: 10.1006/jmsp.1997.7436] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
We present a systematic technique for the calculation of quantum potentials which fit experimentally specified transition spectra. With the aid of examples involving the molecular torsion of single-top molecules, we show how via a very small number of iterations, the observed spectrum may be approached to within a minimal deviation. Copyright 1997 Academic Press. Copyright 1997Academic Press
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Affiliation(s)
- WE Mellor
- Faculty of Science and Technology, La Trobe University, Bundoora, Victoria, 3083, Australia
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Neumann M, Johnson MR. Methyl group tunneling—A quantitative probe of atom–atom potentials. J Chem Phys 1997. [DOI: 10.1063/1.474527] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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The origin and temperature dependence of the single particle, methyl-group rotational potential in acetic acid. Chem Phys 1997. [DOI: 10.1016/s0301-0104(96)00367-9] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Johnson M, Frick B, Trommsdorff H. A high resolution, inelastic neutron scattering investigation of tunnelling methyl groups in aspirin. Chem Phys Lett 1996. [DOI: 10.1016/0009-2614(96)00622-7] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Lee A, Kalotas T, Mellor W. A simplified approach to the calculation of molecular torsion energy levels. Chem Phys Lett 1995. [DOI: 10.1016/0009-2614(95)00871-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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