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    A Series of Crystallographically Characterized Linear and Branched σ-Alkane Complexes of Rhodium: From Propane to 3-Methylpentane

    Bukvic, Alexander J. and Burnage, Arron L. and Tizzard, Graham J. and Martínez-Martínez, Antonio J. and McKay, Alasdair I. and Rees, Nicholas H. and Tegner, Bengt E. and Krämer, Tobias and Fish, Heather and Warren, Mark R. and Coles, Simon J. and Macgregor, Stuart A. and Weller, Andrew S. (2021) A Series of Crystallographically Characterized Linear and Branched σ-Alkane Complexes of Rhodium: From Propane to 3-Methylpentane. Journal of the American Chemical Society, 143 (13). pp. 5106-5120. ISSN 0002-7863

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    Using solid-state molecular organometallic (SMOM) techniques, in particular solid/gas single-crystal to single-crystal reactivity, a series of σ-alkane complexes of the general formula [Rh(Cy PCH CH PCy )(η :η -alkane)][BAr ] have been prepared (alkane = propane, 2-methylbutane, hexane, 3-methylpentane; Ar = 3,5-(CF ) C H ). These new complexes have been characterized using single crystal X-ray diffraction, solid-state NMR spectroscopy and DFT computational techniques and present a variety of Rh(I)···H-C binding motifs at the metal coordination site: 1,2-η :η (2-methylbutane), 1,3-η :η (propane), 2,4-η :η (hexane), and 1,4-η :η (3-methylpentane). For the linear alkanes propane and hexane, some additional Rh(I)···H-C interactions with the geminal C-H bonds are also evident. The stability of these complexes with respect to alkane loss in the solid state varies with the identity of the alkane: from propane that decomposes rapidly at 295 K to 2-methylbutane that is stable and instead undergoes an acceptorless dehydrogenation to form a bound alkene complex. In each case the alkane sits in a binding pocket defined by the {Rh(Cy PCH CH PCy )} fragment and the surrounding array of [BAr ] anions. For the propane complex, a small alkane binding energy, driven in part by a lack of stabilizing short contacts with the surrounding anions, correlates with the fleeting stability of this species. 2-Methylbutane forms more short contacts within the binding pocket, and as a result the complex is considerably more stable. However, the complex of the larger 3-methylpentane ligand shows lower stability. Empirically, there therefore appears to be an optimal fit between the size and shape of the alkane and overall stability. Such observations are related to guest/host interactions in solution supramolecular chemistry and the holistic role of 1°, 2°, and 3° environments in metalloenzymes.

    Item Type: Article
    Additional Information: Cite as: Alexander J. Bukvic, Arron L. Burnage, Graham J. Tizzard, Antonio J. Martínez-Martínez, Alasdair I. McKay, Nicholas H. Rees, Bengt E. Tegner, Tobias Krämer, Heather Fish, Mark R. Warren, Simon J. Coles, Stuart A. Macgregor, and Andrew S. Weller Journal of the American Chemical Society 2021 143 (13), 5106-5120 DOI: 10.1021/jacs.1c00738
    Keywords: molecular organometallic (SMOM) techniques; alkane binding energy; supramolecular chemistry;
    Academic Unit: Faculty of Science and Engineering > Chemistry
    Faculty of Science and Engineering > Research Institutes > Hamilton Institute
    Item ID: 17437
    Identification Number:
    Depositing User: Tobias Kraemer
    Date Deposited: 17 Aug 2023 11:03
    Journal or Publication Title: Journal of the American Chemical Society
    Publisher: American Chemical Society
    Refereed: Yes
    Use Licence: This item is available under a Creative Commons Attribution Non Commercial Share Alike Licence (CC BY-NC-SA). Details of this licence are available here

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