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Limbach HH, Buntkowsky G, Matthes J, Gründemann S, Pery T, Walaszek B, Chaudret B. Novel Insights into the Mechanism of the Ortho/Para Spin Conversion of Hydrogen Pairs: Implications for Catalysis and Interstellar Water. Chemphyschem 2006; 7:551-4. [PMID: 16493700 DOI: 10.1002/cphc.200500559] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The phenomenon of exchange coupling is taken into account in the description of the magnetic nuclear spin conversion between bound ortho- and para-dihydrogen. This conversion occurs without bond breaking, in contrast to the chemical spin conversion. It is shown that the exchange coupling needs to be reduced so that the corresponding exchange barrier can increase and the given magnetic interaction can effectively induce a spin conversion. The implications for related molecules such as water are discussed. For ice, a dipolar magnetic conversion and for liquid water a chemical conversion are predicted to occur within the millisecond timescale. It follows that a separation of water into its spin isomers, as proposed by Tikhonov and Volkov (Science 2002, 296, 2363), is not feasible. Nuclear spin temperatures of water vapor in comets, which are smaller than the gas-phase equilibrium temperatures, are proposed to be diagnostic for the temperature of the ice or the dust surface from which the water was released.
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Affiliation(s)
- Hans-Heinrich Limbach
- Institut für Chemie und Biochemie, Freie Universität Berlin, Takustrasse 3, 14195 Berlin, Germany.
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Matthes J, Pery T, Gründemann S, Buntkowsky G, Sabo-Etienne S, Chaudret B, Limbach HH. Bridging the gap between homogeneous and heterogeneous catalysis: ortho/para H(2) conversion, hydrogen isotope scrambling, and hydrogenation of olefins by Ir(CO)Cl(PPh(3))(2). J Am Chem Soc 2004; 126:8366-7. [PMID: 15237979 DOI: 10.1021/ja0475961] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Some transition metal complexes are known to catalyze ortho/para hydrogen conversion, hydrogen isotope scrambling, and hydrogenation reactions in liquid solution. Using the example of Vaska's complex, we present here evidence by NMR that the solvent is not necessary for these reactions to occur. Thus, solid frozen solutions or polycrystalline powdered samples of homogeneous catalysts may become heterogeneous catalysts. Comparative liquid- and solid-state studies provide novel insight into the reaction mechanisms.
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Affiliation(s)
- Jochen Matthes
- Institute of Chemistry, Freie Universität Berlin, Takustrasse 3, D-14195 Berlin, Germany
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Limbach HH, Ulrich S, Gründemann S, Buntkowsky G, Sabo-Etienne S, Chaudret B, Kubas GJ, Eckert J. NMR and INS Line Shapes of Transition Metal Hydrides in the Presence of Coherent and Incoherent Dihydrogen Exchange. J Am Chem Soc 1998. [DOI: 10.1021/ja962903r] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Hans-Heinrich Limbach
- Contribution from the Institut für Organische Chemie der Freien Universität Berlin, Takustrasse 3, D-14195 Berlin, Germany, the Laboratoire de Chimie de Coordination du CNRS (UP 8241), 205, route de Narbonne, F-31077 Toulouse-Cedex, France, and LANSCE, Los Alamos National Laboratory, Los Alamos, Mail Stop H805, New Mexico 87545
| | - Stefan Ulrich
- Contribution from the Institut für Organische Chemie der Freien Universität Berlin, Takustrasse 3, D-14195 Berlin, Germany, the Laboratoire de Chimie de Coordination du CNRS (UP 8241), 205, route de Narbonne, F-31077 Toulouse-Cedex, France, and LANSCE, Los Alamos National Laboratory, Los Alamos, Mail Stop H805, New Mexico 87545
| | - Stephan Gründemann
- Contribution from the Institut für Organische Chemie der Freien Universität Berlin, Takustrasse 3, D-14195 Berlin, Germany, the Laboratoire de Chimie de Coordination du CNRS (UP 8241), 205, route de Narbonne, F-31077 Toulouse-Cedex, France, and LANSCE, Los Alamos National Laboratory, Los Alamos, Mail Stop H805, New Mexico 87545
| | - Gerd Buntkowsky
- Contribution from the Institut für Organische Chemie der Freien Universität Berlin, Takustrasse 3, D-14195 Berlin, Germany, the Laboratoire de Chimie de Coordination du CNRS (UP 8241), 205, route de Narbonne, F-31077 Toulouse-Cedex, France, and LANSCE, Los Alamos National Laboratory, Los Alamos, Mail Stop H805, New Mexico 87545
| | - Sylviane Sabo-Etienne
- Contribution from the Institut für Organische Chemie der Freien Universität Berlin, Takustrasse 3, D-14195 Berlin, Germany, the Laboratoire de Chimie de Coordination du CNRS (UP 8241), 205, route de Narbonne, F-31077 Toulouse-Cedex, France, and LANSCE, Los Alamos National Laboratory, Los Alamos, Mail Stop H805, New Mexico 87545
| | - Bruno Chaudret
- Contribution from the Institut für Organische Chemie der Freien Universität Berlin, Takustrasse 3, D-14195 Berlin, Germany, the Laboratoire de Chimie de Coordination du CNRS (UP 8241), 205, route de Narbonne, F-31077 Toulouse-Cedex, France, and LANSCE, Los Alamos National Laboratory, Los Alamos, Mail Stop H805, New Mexico 87545
| | - Gregory J. Kubas
- Contribution from the Institut für Organische Chemie der Freien Universität Berlin, Takustrasse 3, D-14195 Berlin, Germany, the Laboratoire de Chimie de Coordination du CNRS (UP 8241), 205, route de Narbonne, F-31077 Toulouse-Cedex, France, and LANSCE, Los Alamos National Laboratory, Los Alamos, Mail Stop H805, New Mexico 87545
| | - Jürgen Eckert
- Contribution from the Institut für Organische Chemie der Freien Universität Berlin, Takustrasse 3, D-14195 Berlin, Germany, the Laboratoire de Chimie de Coordination du CNRS (UP 8241), 205, route de Narbonne, F-31077 Toulouse-Cedex, France, and LANSCE, Los Alamos National Laboratory, Los Alamos, Mail Stop H805, New Mexico 87545
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Buntkowsky G, Limbach HH, Wehrmann F, Sack I, Vieth HM, Morris RH. 2H NMR Theory of Transition Metal Dihydrides: Coherent and Incoherent Quantum Dynamics. J Phys Chem A 1997. [DOI: 10.1021/jp970103c] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Gerd Buntkowsky
- Institut für Organische Chemie and Institut für Experimentalphysik der Freie Universität Berlin, Takustrasse 3, D-14195 Berlin, Germany, and Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario, Canada M5S 3H6
| | - Hans-Heinrich Limbach
- Institut für Organische Chemie and Institut für Experimentalphysik der Freie Universität Berlin, Takustrasse 3, D-14195 Berlin, Germany, and Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario, Canada M5S 3H6
| | - Frank Wehrmann
- Institut für Organische Chemie and Institut für Experimentalphysik der Freie Universität Berlin, Takustrasse 3, D-14195 Berlin, Germany, and Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario, Canada M5S 3H6
| | - Ingolf Sack
- Institut für Organische Chemie and Institut für Experimentalphysik der Freie Universität Berlin, Takustrasse 3, D-14195 Berlin, Germany, and Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario, Canada M5S 3H6
| | - Hans-Martin Vieth
- Institut für Organische Chemie and Institut für Experimentalphysik der Freie Universität Berlin, Takustrasse 3, D-14195 Berlin, Germany, and Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario, Canada M5S 3H6
| | - Robert H. Morris
- Institut für Organische Chemie and Institut für Experimentalphysik der Freie Universität Berlin, Takustrasse 3, D-14195 Berlin, Germany, and Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario, Canada M5S 3H6
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Buntkowsky G, Bargon J, Limbach HH. A Dynamic Model of Reaction Pathway Effects on Parahydrogen-Induced Nuclear Spin Polarization. J Am Chem Soc 1996. [DOI: 10.1021/ja954188b] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Gerd Buntkowsky
- Contribution from the Institut für Organische Chemie der Freien Universität Berlin, Takustrasse 3, D-14195 Berlin, and Institut für Physikalische Chemie der Universität Bonn, Wegelerstrasse 12, D-53115 Bonn, Germany
| | - Joachim Bargon
- Contribution from the Institut für Organische Chemie der Freien Universität Berlin, Takustrasse 3, D-14195 Berlin, and Institut für Physikalische Chemie der Universität Bonn, Wegelerstrasse 12, D-53115 Bonn, Germany
| | - Hans-Heinrich Limbach
- Contribution from the Institut für Organische Chemie der Freien Universität Berlin, Takustrasse 3, D-14195 Berlin, and Institut für Physikalische Chemie der Universität Bonn, Wegelerstrasse 12, D-53115 Bonn, Germany
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