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Carbon–hydrogen bond activation

Carbon–hydrogen bond activation or C-H activation is a reaction that breaks a carbon–hydrogen bond. Most times, the reaction involves organometallic complexes. The reaction path has coordination of a hydrocarbon to the inner-sphere of the metal atom (“M”). The reaction path includes either an intermediate “alkane or arene complex” or as a transition state leading to a "M-C" intermediate.[1][2][3] The reaction path makes C-H activation different from other reactions. During the C-H breaking event the hydrocarbyl group remains linked in the inner-sphere and under the influence of the metal atom.

Chemists study C-H activation because for many years chemists believed that C-H bonds were unreactive. Both theoretical studies as well as experiments now show that C-H bonds can be broken. This is done by a nearby metal atom changing the electron distribution of the C-H bond (coordination). Much chemical research looks at the design and synthesis of new reagents and catalysts that can affect C-H activation. The goal of this research is the conversion of cheap and abundant alkanes into valuable functionalized organic compounds.

Historians say that Otto Dimroth discovered the first C-H activation reaction. In 1902, he reported that benzene reacted with mercury(II) acetate (See: organomercury), but some scholars do not view this reaction as being a C-H activation. Goldman & Goldberg[1] later wrote, C-H activation looks like H-H activation: both can be achieved by electrophilic or oxidative addition. The first true C-H activation reaction was reported by Joseph Chatt in 1965[4] with insertion of a ruthenium atom ligated to dmpe in the C-H bond of naphthalene.

Carbon–hydrogen Bond Activation Media

  • Cobalt-catalyzed C-H activation

  • Fujiwara's palladium- and copper-catalyzed C-H functionalization

  • C–H activation by Bergman et al. (left) and Graham et al.

  • C–H activation of pentane, as seen in Ledgzdins et al., J. Am. Chem. Soc. 2007; 129, 5372–3.

  • Murai reaction; X = directing group.

  • Mechanism for Pd-catalyzed C-H activation

  • Hartwig borylation

  • Ru catalyst based borylation

  • C–H Bond activation Periana 1998

  • Methyl phenyldiazoacetate is the precursor for asymmetric C-H activation viadonor-acceptor carbene using a chiral dirhodium catalyst.

References

  1. ↑ 1.0 1.1 Organometallic C-H Bond Activation: An Introduction Alan S. Goldman and Karen I. Goldberg ACS Symposium Series 885, Activation and Functionalization of C-H Bonds, 2004, 1–43
  2. ↑ Arndtsen, B. A.; Bergman, R. G.; Mobley, T. A.; Peterson, T. H. “Selective Intermolecular Carbon–Hydrogen Bond Activation by Synthetic Metal Complexes in Homogeneous Solution.” Accounts of Chemical Research, 1995: 28 (3) 154–162.
  3. ↑ Periana, R. A.; Bhalla, G.; Tenn, W. J., III, Young, K. J. H.; Liu, X. Y.; Mironov, O.; Jones, C.; Ziatdinov, V. R. “Perspectives on some challenges and approaches for developing the next generation of selective, low temperature, oxidation catalysts for alkane hydroxylation based on the C-H activation reaction.” Journal of Molecular Catalysis A: Chemical, 2004: 220 (1) 7–25. doi:10.1016/j.molcata.2004.05.036
  4. ↑ The tautomerism of arene and ditertiary phosphine complexes of ruthenium(0), and the preparation of new types of hydrido-complexes of ruthenium(II) J. Chatt and J. M. Davidson, J. Chem. Soc. 1965, 843 doi:10.1039/JR9650000843

Further reading

  • “Activation of C-H Bonds by Metal Complexes”, A. E. Shilov, G. B. Shul’pin, Chem. Rev. 1997, 97, 2879–2932. doi:10.1021/cr9411886
  • “Activation and Catalytic Reactions of Saturated Hydrocarbons in the Presence of Metal Complexes”, A. E. Shilov, G. B. Shul’pin, Kluwer Academic Publishers, Dordrecht/Boston/London, 2000 (552 p) (Springer, ISBN 978-0-7923-6101-5). https://www.springer.com/chemistry/physical+chemistry/book/978-0-7923-6101-5
  • “Alkane C-H activation and functionalization with homogeneous transition metal catalysts: a century of progress – a new millennium in prospect”, R. H. Crabtree, J. Chem. Soc., Dalton Trans. 2001, 17, 2437–2450. doi:10.1039/B103147N
  • “Organometallic alkane CH activation”, R. H. Crabtree, J. Organometal. Chem. 2004, 689, 4083–4091. doi:10.1016/j.jorganchem.2004.07.034
  • “Mechanistic Aspects of C−H Activation by Pt Complexes”, M. Lersch, M.Tilset, Chem. Rev. 2005, 105, 2471−2526. doi:10.1021/cr030710y
  • “Recent Advances in the Platinum-mediated CH Bond Functionalization”, A. N. Vedernikov, Curr. Org. Chem. 2007, 11, 1401−1416.
  • “Catalytic C-H functionalization by metalcarbenoid and nitrenoid insertion”, H. M. L. Davies, J. R. Manning, Nature, 2008, 451, 417−424, doi:10.1038/nature06485
  • "Mechanisms of C-H bond activation: rich synergy between computation and experiment”, Y. Boutadla, D. L. Davies, S. A. Macgregor, A. I. Poblador-Bahamonde, Dalton Trans. 2009, 5820−5831. doi:10.1039/B904967C
  • “C-H Bond Activation in Transition Metal Species from a Computational Perspective”, D. Balcells, E. Clot, O. Eisenstein, Chem. Rev. 2010, 110, 749–823. doi:10.1021/cr900315k
  • “Palladium-Catalyzed Ligand-Directed C-H Functionalization Reactions”, T. W. Lyons, M. S. Sanford, Chem. Rev. 2010, 110, 1147–1169. doi:10.1021/cr900184e
  • “Selectivity enhancement in functionalization of C-H bonds: A review”, G. B. Shul’pin, Org. Biomol. Chem. 2010, 8, 4217–4228. doi:10.1039/c004223d


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