Despite their widespread application in catalysis, material science and biomedical research,¹ the development of gold(III) complexes remains limited by challenges associated with their synthesis. The use of bidentate and tridentate ligands is crucial to prevent the facile reduction to gold(I) or decomposition to elemental gold(0). However, most of the existing protocols to access both, mono and bis-cycloaurated complexes rely on harsh conditions and/or require the use of toxic reagents (e.g. Hg or Sn).² On the other hand, organoborane compounds have been efficiently used in stoichiometric and catalytic transmetalation reactions to gold(III),³ making them an appealing class of functional groups to direct the cyclometalation step.

In this work, we have developed a novel and environmentally-friendly approach to access gold(III) complexes via boron-mediated transmetalation.⁴ A late-stage functionalization strategy allows the incorporation of boronic ester groups onto a wide array of (N^C) and (N^C^C) ligands. The X-ray diffraction analysis of the B(OR)₂-functionalized ligands reveals the presence of a B-N dative bond, crucial in stabilizing the substrates while promoting the transmetalation. The desired transformation could be achieved under remarkably mild conditions with a broad functional group tolerance, affording mono- and bis-cyclometalated gold(III) complexes in moderate to very good yields. Furthermore, the expansion of this method to the synthesis of (C^N^C)Au(III) complexes has been successfully achieved.

[1] L. Rocchigiani, M. Bochmann, Chemical Reviews, 2021, 121, 8364-8451.

[2] R. Kumar, C. Nevado, Angewandte Chemie International Edition, 2017, 56, 1994-2015.

[3] M. Joost, A. Amgoune, D. Bourissou, Angewandte Chemie International Edition, 2015, 54, 15022-15045.

[4] Manuscript submitted. D. Chauvin, P. Font, B. Pires, J. Martín, X. Ribas, C. Nevado.