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Bond Shift Rearrangement of Chloro-, Bromo-, and Iodobullvalene in the Solid State and in Solution. A Carbon-13 and Proton NMR Study

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Contribution from the Department of Chemical Physics, The Weizmann Institute of Science, Rehovot 76100, Israel, Institut für Physikalische Chemie, Universität Stuttgart, Pfaffenwaldring 55, D-7000 Stuttgart 80, Germany, and Max-Planck-Institut für Medizinische Forschung, A.G. Molekülkristalle, Jahnstrasse 29, 69120 Heidelberg, Germany
Cite this: J. Am. Chem. Soc. 1998, 120, 22, 5526–5538
Publication Date (Web):May 20, 1998
https://doi.org/10.1021/ja9728029
Copyright © 1998 American Chemical Society
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Abstract

The mechanisms of the Cope rearrangement in chloro-, bromo-, and iodobullvalene in solution and in the solid state were investigated by NMR techniques. The dominant species in solution, for all three compounds, are isomers 2 and 3 with nearly equal concentrations (where the numbers refer to the substituted carbons in the bullvalene moiety). The kinetics of the rearrangement processes as studied by 1H and 13C NMR involve three dominant bond shift rearrangements:  interconversion between isomers 2 and 3, degenerate rearrangement of isomer 2, and a pseudodegenerate rearrangement of isomer 3, with isomer 1 serving as an intermediate. The solid state properties of these compounds were studied by carbon-13 MAS NMR and the bromo and iodo derivatives also by X-ray crystallography. Bromo- and iodobullvalene crystallize entirely as isomer 2 in the orthorhombic Fdd2 space group. The molecules in the crystals are orientationally disordered, and the carbon-13 results show that this disorder is dynamic on the NMR time scale. Rotor-synchronized two-dimension exchange spectroscopy, magnetization transfer experiments, and analysis of dynamic MAS spectra show that the mechanism of the dynamic disorder involves a degenerate rearrangement of isomer 2 which results in an effective π-flip of the molecule in the crystal. The Arrhenius activation parameters for this process are ΔE = 57.1 kJ/mol, A = 5.2 × 1012 s-1 for bromobullvalene and ΔE = 58.5 kJ/mol, A = 1.8 × 1013 s-1 for iodobullvalene. Chlorobullvalene is liquid at room temperature (mp 14 °C). Upon cooling of this compound in the MAS probe to well below 0 °C, signals due to both isomer 2 and isomer 3 are observed in the solid state. It is not known whether the solid so obtained is a frozen glass, a mixture of crystals due to, respectively, isomer 2 and isomer 3, or a single type of crystals consisting of a stoichiometric mixture of both isomers. Rotor-synchronized two-dimensional exchange measurements show that the chlorobullvalene isomers in this solid undergo Cope rearrangement. However, the bond shift processes involve only a degenerate rearrangement of isomer 2 and a pseudodegenerate rearrangement of isomer 3. No cross-peaks corresponding to interconversion between the two isomers are observed.

*

In papers with more than one author, the asterisk indicates the name of the author to whom inquiries about the paper should be addressed.

 The Weizmann Institute of Science.

 Universität Stuttgart.

§

 Max-Planck-Institut für Medizinische.

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  8. Sofia Ferrer, Antonio M. Echavarren. Synthesis of Barbaralones and Bullvalenes Made Easy by Gold Catalysis. Angewandte Chemie International Edition 2016, 55 (37) , 11178-11182. https://doi.org/10.1002/anie.201606101
  9. William Acree, James S. Chickos. Phase Transition Enthalpy Measurements of Organic and Organometallic Compounds. Sublimation, Vaporization and Fusion Enthalpies From 1880 to 2015. Part 1. C 1 − C 10. Journal of Physical and Chemical Reference Data 2016, 45 (3) , 033101. https://doi.org/10.1063/1.4948363
  10. Cory M. Widdifield, Rebecca P. Chapman, David L. Bryce. Chapter 5 Chlorine, Bromine, and Iodine Solid-State NMR Spectroscopy. 2009,,, 195-326. https://doi.org/10.1016/S0066-4103(08)00405-5
  11. David L. Bryce, Gregory D. Sward. Solid-state NMR spectroscopy of the quadrupolar halogens: chlorine-35/37, bromine-79/81, and iodine-127. Magnetic Resonance in Chemistry 2006, 44 (4) , 409-450. https://doi.org/10.1002/mrc.1741
  12. D. Reichert. NMR Studies of Dynamic Processes in Organic Solids. 2005,,, 159-203. https://doi.org/10.1016/S0066-4103(04)55003-2
  13. James S Chickos, William E Acree. Total phase change entropies and enthalpies. Thermochimica Acta 2002, 395 (1-2) , 59-113. https://doi.org/10.1016/S0040-6031(02)00213-7
  14. Christian Jäger, Detlef Reichert, Herbert Zimmermann, Tapas Sen, Raphy Poupko, Zeev Luz. Bond-Shift Rearrangement in Solid Li3P7(Monoglyme)3: A 31P MAS NMR Study. Journal of Magnetic Resonance 2001, 153 (2) , 227-237. https://doi.org/10.1006/jmre.2001.2446
  15. Detlef Reichert, Günter Hempel, Horst Schneider, Herbert Zimmermann, Zeev Luz. Dynamic Carbon-13 MAS NMR: Application to Benzene Ring Flips in Polyaryl Ethers. Solid State Nuclear Magnetic Resonance 2000, 18 (1-4) , 17-36. https://doi.org/10.1006/snmr.2000.0008
  16. Z. LUZ, L. OLIVIER, R. POUPKO, K. MUELLER, C. KRIEGER, H. ZIMMERMANN. ChemInform Abstract: Bond Shift Rearrangement of Chloro-, Bromo-, and Iodobullvalene in the Solid State and in Solution. A Carbon-13 and Proton NMR Study.. ChemInform 1998, 29 (40) , no-no. https://doi.org/10.1002/chin.199840044

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