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Profiling an Optimal Pt(II) Based Methane Activation Catalyst by Density Functional Theory

Profiling an Optimal Pt(II) Based Methane Activation Catalyst by Density Functional Theory. Hongjuan Zhu, Tom Ziegler Department of Chemistry University of Calgary May 28, 2008. Methane Activation. Energy-intensive, two-step process. Direct oxidation process.

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Profiling an Optimal Pt(II) Based Methane Activation Catalyst by Density Functional Theory

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  1. Profiling an Optimal Pt(II) Based Methane Activation Catalyst by Density Functional Theory Hongjuan Zhu, Tom Ziegler Department of Chemistry University of Calgary May 28, 2008

  2. Methane Activation Energy-intensive, two-step process Direct oxidation process S. S. Stahl, J. A. Labinger, J. E. Bercaw, Angew. Chem. Int. Ed.1998, 37, 2180

  3. Shilov Reactions Improve catalyst efficiency? Aleksandre Evgen’yevich Shilov N. F. Gol’dshleger, M. B. Tyabin, A. E. Shilov, A. A. Shteinman, Zh. Fiz. Khim. (Engl. Transl.)1969, 43, 1222 N. F. Gol’dshleger, V. V. Es’kova, A. E. Shilov, A. A. Shteinman, Zh. Fiz. Khim. (Engl. Transl.)1972, 46, 785

  4. N. F. Gol’dshleger, M. B. Tyabin, A. E. Shilov, A. A. Shteinman, Zh. Fiz. Khim. (Engl. Transl.)1969, 43, 1222

  5. Outline • Determining factor for the energy barrier of methane coordination • Determining factor for the energy barrier of C-H bond cleavage • How to balance the two energy barriers to obtain optimal Pt(II) catalyst

  6. Methane Coordination H. Zhu, T. Ziegler, Organometallics 2007, 26, 2277 H. Zhu, T. Ziegler, J. Organomet. Chem.2006, 691, 4486

  7. Methane Coordination Geometry of TS(1-2)

  8. Methane Coordination

  9. C-H Bond Cleavage H. Zhu, T. Ziegler, Organometallics 2007, 26, 2277 H. Zhu, T. Ziegler, Organometallics 2008, in press

  10. Pt-methane intermediate Transition State of C-H bond cleavage C-H Bond Cleavage

  11. C-H Bond Cleavage

  12. Facilitation of the replacement or substitution of a second ligand trans to the first by an external ligand Trans Effect R. H. Crabtree, The Organometallic Chemistry of the Transition Metals; Wiley: New York (1998)

  13. Optimal Pt(II) catalyst • Trans ligand T affects the two energy barriers in opposite directions • Too weak or too strong trans ligand T would make one energy barrier dominate. • Optimal Pt(II) catalyst should have medium trans ligand T because medium T would reduce the first energy barrier while still keep the second one relatively lower

  14. Conclusions • The determining factor for the energy barriers of both methane coordination and C-H bond activation is the trans ligand T, which changes the two energy barriers in opposite directions • Optimal Pt(II) catalyst for the Shilov reaction can be obtained by using ligand T with medium trans directing ability

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