- Au(III)-substituted carbenes: in the frame of WP3 dealing with Au(IV) complexes, we have been interested in the dichotomy between Au(III)-substituted carbenes and Au(V) carbyne complexes. Au(IV)-substituted radicals are a further electromeric form for these species. (WP3). The targeted compounds were generated by photolysis of Au(III)-substituted diazo compounds equipped with a rigid N^C^C pincer ligand at Au(III). When substituted by a sterically demanding aryl group (Dmp), the carbene proved only transient and evolved by intramolecular C–H insertion followed by β-H elimination. Steric shielding prevents intermolecular carbene trapping. The related SiMe3-substituted carbene was generated and characterized by in crystallo photolysis. In solution, we evidenced intermolecular reactivity typical for triplet as well as singlet carbenes such as H atom abstraction and carbene-type couplings with isocyanides. DFT calculations shed light into the structure, bonding and reactivity of these Au(III)-substituted carbenes. These findings demonstrate the potential of Au(III) fragments as powerful, electronically spectator substituents for accessing and modulating highly reactive species. Due to the absence of strong π-interactions, the carbene center remains largely unperturbed electronically and exhibits rich reactivity. Manuscript submitted to J. Am. Chem. Soc., in revision.
- Fake Au(IV) complexes: in the frame of WP3 and WP4, we have prepared and fully characterized the first Au(III) semi-quinones complexes. They proved stable at room temperature for hours to days. Knowing this, we took advantage of the square-planar geometry and electron-rich nature of Au(III) catecholate complexes to form EDA adducts with organic substrates (diazonium / thianthrenium salts) and induce photochemically single-electron transfer to generate aryl radicals using blue/green lights. First proof-of-concepts of photocatalysis were obtained in the arylation of furanes. The generality of the approach was then substantiated with aryl thianthrenium salts (much more attractive synthetically as they are prepared by simple C–H activation) and a variety of C–C and C–X coupling reactions. Detailed mechanistic studies have been initiated, both experimentally and computationally. A variety of Au(III) complexes (with different ancillary and redox-active ligands) seems to work, which offer a very powerful handle to tune the photophysical, photochemical and redox properties, and thereby address synthetically important but challenging transformations. A first paper is under preparation with the first results and it will be submitted beginning of 2026.
