A bonding model for gold(I) carbene complexes

Abstract

The last decade has witnessed dramatic growth in the number of reactions catalysed by electrophilic gold complexes. Although proposed mechanisms often invoke the intermediacy of gold-stabilized cationic species, the nature of bonding in these intermediates remains unclear. Herein, we propose that the carbon–gold bond in these intermediates comprises varying degrees of both σ- and π-bonding; however, the overall bond order is generally less than or equal to one. The bonding in a given gold-stabilized intermediate, and the position of this intermediate on a continuum ranging from gold-stabilized singlet carbene to gold-coordinated carbocation is dictated by the carbene substituents and the ancillary ligand. Experiments show that the correlation between bonding and reactivity is reflected in the yield of gold-catalysed cyclopropanation reactions.

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Figure 1: Calculated and experimental activation energies to bond rotation (indicated with arrows).
Figure 2: Structural and electronic comparison of cationic metal-free and [AuPMe3]+ substituted substrates.
Figure 3: Experimental and theoretical comparison for the carbene reactivity of the substrate with different ancillary ligands.
Figure 4: Arrow pushing in the formation of gold-stabilized carbenes.

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Acknowledgements

F.D.T. acknowledges NIHGMS, Bristol-Myers Squibb and Novartis for funding, and J. Matthey for the donation of AuCl3. The MSC computational facilities were funded by grants from ARO-DURIP and ONR-DURIP. D.B. and E.T. thank R. Nielsen for useful suggestions.

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D.B., N.D.S. and F.D.T. originated the idea and wrote the manuscript, N.D.S. and Y.W. performed the experiments, D.B. and E.T. performed the calculations, all authors contributed to discussions and edited the manuscript. D.B. and N.D.S. contributed equally to this work.

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Correspondence to F. Dean Toste.

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Benitez, D., Shapiro, N., Tkatchouk, E. et al. A bonding model for gold(I) carbene complexes. Nature Chem 1, 482–486 (2009). https://doi.org/10.1038/nchem.331

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