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Structural snapshots of concerted double E–H bond activation at a transition metal centre

Nature Chemistry volume 9, pages 1256–1262 (2017)Cite this article

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A Corrigendum to this article was published on 23 January 2018

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Abstract

Bond activation at a transition metal centre is a key fundamental step in numerous chemical transformations. The oxidative addition of element–hydrogen bonds, for example, represents a critical step in a range of widely applied catalytic processes. Despite this, experimental studies defining steps along the bond activation pathway are very rare. In this work, we report on fundamental studies defining a double oxidative activation pathway: combined experimental and computational approaches yield structural snapshots of the simultaneous activation of both bonds of a β-diketiminate-stabilized GaH2 unit at a single metal centre. Systematic variation of the supporting phosphine ligands and single crystal X-ray/neutron diffraction are exploited in tandem to allow structural visualization of the activation process, from a η2-H,H σ-complex showing little Ga–H bond activation, through species of intermediate geometry featuring stretched Ga–H and compressed M–H/M–Ga bonds, to a fully activated metal dihydride featuring a neutral (carbene-type) N-heterocyclic GaI ligand.

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Figure 1: Single–step oxidative activation of one or two E–H bonds at a single metal centre (shown for E = a group 13 element)21,22.
Figure 2: Syntheses of 2-dppp, 2-dcype, 2-dcypp and 2-PCy3 from the corresponding [(phosphine)2Rh]+ containing precursors (counter-anions omitted for clarity).
Figure 3: Molecular structures of the cationic components as determined by X-ray diffraction.
Figure 4: Key orbital interactions between the [(dppp)Rh]+ and (NacNac)DippGaH2 fragments in 2-dppp calculated using an ETS-NOCV analysis22,58.
Figure 5: A possible energetic pathway for the [(Cy3P)2Rh]+ system linking an η2-H,H σ-complex to a six-coordinate (agostically supported) RhIII dihydride.

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  • 18 December 2017

    References 23–27 and 31–38 in the introductory paragraphs describe literature precedent for the activation of two E–H bonds at a transition metal centre for E = B or C). It should be noted that experimental precedent also exists for the analogous activation of Si–H bonds and the manuscript has been modified to include additional citation of this chemistry (refs 22, 28–30). References 22. Lipke, M. C., Liberman-Martin, A. L. & Tilley, T. D. Electrophilic activation of silicon–hydrogen bonds in catalytic hydrosilations. Angew. Chem. Int. Ed. 56, 2260–2294 (2017). 28. Thomas, C. M. & Peters, J. C. An η3-H2SiR2 adduct of [{PhB(CH2PiP2)3}FeH. Angew. Chem. Int. Ed. 45, 776–780 (2006). 29. Faluso, M. E., Glaser, P. B. & Tilley, T. D. Cp*;(PiPr3)RuOTf: a reagent for access to ruthenium silylene complexes. Organometallics 30, 5524–5531 (2011). 30. Faluso, M. E., Lipke, M. C. & Tilley, T. D. Structural and mechanistic investigation of a cationic hydrogen-substituted ruthenium silylene catalyst for alkene hydrosilation. Chem. Sci. 4, 3882–3887 (2013).

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Acknowledgements

This work was supported by the EPSRC (studentship to J.A.B.A.); ANSTO is thanked for the allocation of discretionary neutron beam-time on KOALA to proposal DB3706 and a further allocation to proposal P3932. C.S. thanks the Alexander von Humboldt Stiftung for a Feodor Lynen Fellowship.

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Authors and Affiliations

  1. Department of Chemistry, Inorganic Chemistry Laboratory, University of Oxford, South Parks Road, Oxford, OX1 3QR, UK

    Joseph A. B. Abdalla, Alexa Caise, Christian P. Sindlinger, Rémi Tirfoin, Amber L. Thompson & Simon Aldridge

  2. Australian Centre for Neutron Scattering, Australian Nuclear Science and Technology Organization, New Illawarra Road, Lucas Heights, 2234, New South Wales, Australia

    Alison J. Edwards

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Contributions

J.A.B.A. and A.C. synthesized and characterized the compounds. R.T., A.J.E. and A.L.T. collected the single-crystal X-ray and neutron crystallographic data and determined the crystal structures. J.A.B.A. and C.P.S. carried out the DFT calculations. S.A. generated and managed the project and wrote the manuscript. All authors discussed the results and commented on the manuscript.

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Correspondence to Simon Aldridge.

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Abdalla, J., Caise, A., Sindlinger, C. et al. Structural snapshots of concerted double E–H bond activation at a transition metal centre. Nature Chem 9, 1256–1262 (2017). https://doi.org/10.1038/nchem.2792

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