The Role of Proton Shuttles in the Reversible Activation of Hydrogen via Metal–Ligand Cooperation

Smith, Nicholas E.; Bernskoetter, Wesley H.; Hazari, Nilay

doi:10.1021/jacs.9b09062

Title: The Role of Proton Shuttles in the Reversible Activation of Hydrogen via Metal–Ligand Cooperation

Abstract

The reversible activation of H₂ via a pathway involving metal–ligand cooperation (MLC) is proposed to be important in many transition metal catalyzed hydrogenation and dehydrogenation reactions. Nevertheless, there is a paucity of experimental information probing the mechanism of this transformation. In this paper, we present an in-depth kinetic study of the 1,2-addition of H₂ via an MLC pathway to the widely used iron catalyst [(^iPrPNP)FeH(CO)] (1) (^iPrPNP = N(CH₂CH₂PⁱPr₂)₂^–). We report one of the first experimental demonstrations of an enhancement in rate for the activation of H₂ using protic additives, which operate as “proton shuttles”. Our results indicate that proton shuttles need to be able to both simultaneously donate and accept a proton, and the best shuttles are molecules that are strong hydrogen bond donors but sufficiently weak acids to avoid deleterious protonation of the transition metal complex. Additionally, comparison of the rate of H₂ activation via an MLC pathway between 1 and two widely used ruthenium catalysts enables more general conclusions about the role of the metal, ancillary ligand, and proton shuttles in H₂ activation. The results of this study provide guidance about the design of catalysts and additives to promote H₂ activation via an MLC pathway.

Authors:

^[1];

^[2];

^[1]

Yale Univ., New Haven, CT (United States)
Univ. of Missouri, Columbia, MO (United States)

Publication Date:: 2019-10-16

Research Org.:: Univ. of Missouri, Columbia, MO (United States)

Sponsoring Org.:: USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Chemical Sciences, Geosciences & Biosciences Division

OSTI Identifier:: 1594892

Grant/Contract Number:: SC0018222

Resource Type:: Accepted Manuscript

Journal Name:: Journal of the American Chemical Society

Additional Journal Information:: Journal Volume: 141; Journal Issue: 43; Journal ID: ISSN 0002-7863

Publisher:: American Chemical Society (ACS)

Country of Publication:: United States

Language:: English

Subject:: 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats


                    Smith, Nicholas E., Bernskoetter, Wesley H., and Hazari, Nilay. The Role of Proton Shuttles in the Reversible Activation of Hydrogen via Metal–Ligand Cooperation.  United States: N. p., 2019. 
        Web.  doi:10.1021/jacs.9b09062.

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                    Smith, Nicholas E., Bernskoetter, Wesley H., & Hazari, Nilay. The Role of Proton Shuttles in the Reversible Activation of Hydrogen via Metal–Ligand Cooperation.  United States.  doi:https://doi.org/10.1021/jacs.9b09062

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                    Smith, Nicholas E., Bernskoetter, Wesley H., and Hazari, Nilay. Wed .  
        "The Role of Proton Shuttles in the Reversible Activation of Hydrogen via Metal–Ligand Cooperation".  United States.  doi:https://doi.org/10.1021/jacs.9b09062.  https://www.osti.gov/servlets/purl/1594892.

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@article{osti_1594892,

  title        = {The Role of Proton Shuttles in the Reversible Activation of Hydrogen via Metal–Ligand Cooperation},

  author       = {Smith, Nicholas E. and Bernskoetter, Wesley H. and Hazari, Nilay},

  abstractNote = {The reversible activation of H2 via a pathway involving metal–ligand cooperation (MLC) is proposed to be important in many transition metal catalyzed hydrogenation and dehydrogenation reactions. Nevertheless, there is a paucity of experimental information probing the mechanism of this transformation. In this paper, we present an in-depth kinetic study of the 1,2-addition of H2 via an MLC pathway to the widely used iron catalyst [(iPrPNP)FeH(CO)] (1) (iPrPNP = N(CH2CH2PiPr2)2–). We report one of the first experimental demonstrations of an enhancement in rate for the activation of H2 using protic additives, which operate as “proton shuttles”. Our results indicate that proton shuttles need to be able to both simultaneously donate and accept a proton, and the best shuttles are molecules that are strong hydrogen bond donors but sufficiently weak acids to avoid deleterious protonation of the transition metal complex. Additionally, comparison of the rate of H2 activation via an MLC pathway between 1 and two widely used ruthenium catalysts enables more general conclusions about the role of the metal, ancillary ligand, and proton shuttles in H2 activation. The results of this study provide guidance about the design of catalysts and additives to promote H2 activation via an MLC pathway.},

  doi          = {10.1021/jacs.9b09062},

  journal      = {Journal of the American Chemical Society},

  number       = 43,

  volume       = 141,

  place        = {United States},

  year         = {2019},

  month        = {10}

}

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DOI: https://doi.org/10.1021/jacs.9b09062

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Title: The Role of Proton Shuttles in the Reversible Activation of Hydrogen via Metal–Ligand Cooperation

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