Homogeneous Gold Redox Chemistry: Organometallics, Catalysis, and Beyond

Abstract

Gold redox chemistry holds the promise of unique reactivities and selectivities that are different to other transition metals. Recent studies have utilized strain release, ligand design, and photochemistry to promote the otherwise sluggish oxidative addition to Au(I) complexes. More details on the reductive elimination from Au(III) complexes have also been revealed. These discoveries have facilitated the development of gold redox catalysis and will continue to offer mechanistic insight and inspiration for other transition metals. This review highlights how research in organometallic chemistry has led to gold redox catalysis, as well as applications in materials science, bioconjugation, and radiochemical synthesis.

Figure 1.. Introduction to Gold Redox Chemistry.

(A) Typical reactivities in gold catalysis; (B) transition-metal-catalyzed cross-coupling; (C) high reduction potential for Au(I/III); (D) studies on gold redox chemistry; and (E) implications of gold redox chemistry.

Figure 2.. Oxidative Addition Reactions Leading to Stable Au(III) Catalysts.

(A) Oxidative addition of an Si–Si bond to an Au(I) complex. (B) Oxidative addition of a C–C bond to an Au(I) complex. (C) Au(III) complexes as efficient Lewis acid catalysts: (i) an Au(III)-catalyzed Mukaiyama–Michael reaction; (ii) an Au(I)/(III)-catalyzed tandem isomerization/Mukaiyama–Michael reaction; and (iii) Au(III)-catalyzed regioselective reactions of unsaturated aldehydes. (D) Migratory insertion of a carbene into an Au(III)–C bond. (E) Chiral Au(III)-catalyzed enantioconvergent kinetic resolution.

Figure 3.. Ligand Designs to Facilitate Oxidative Addition to Au(I) Complexes, Part 1.

(A) Bimetallic Au(I)-catalyzed cross-couplings: (i) allylation of boronic acids; and (ii) oxidative cross-coupling of arylboronates and arylsilanes. (B) Bidentate Au(I)-enabled oxidative addition: (i) schematic design principle; (ii) carborane bisphosphine Au(I)-mediated oxidative addition; and (iii) bipyridyl Au(I)-mediated Negishi-type cross-coupling.

Figure 4.. Ligand Designs to Facilitate Oxidative Addition to Au(I) Complexes, Part 2.

(A) Hemilabile ligand-supported Au(I)-mediated cross-coupling: (i) schematic design principle; (ii) (P,N)-hemilabile ligand-enabled oxidative addition to Au(I); (iii) (P,N)-hemilabile ligand-enabled Au-catalyzed arylation reactions; (iv) (P,N)-hemilabile ligand-enabled Au-catalyzed C–N coupling reaction; (v) (P,N)-hemilabile ligand-enabled Au-catalyzed 1,2-diarylation of alkenes; and (vi) Au(III)-mediated C–S coupling reaction for bioconjugation and nanomaterials.

Figure 5.. Photochemically Triggered Oxidative Addition to Au(I) Complexes.

(A) Photoinitiated oxidative addition of CF₃I to an Au(I) complex. (B) Photoredox gold dual catalysis: (i) an oxyarylation reaction of alkene; (ii) ring expansion–oxidative arylation reaction; and (iii) mechanistic studies of photoredox gold dual catalysis. (C) Photosensitized oxidative addition to an Au(I) complex.

Figure 6.. Other Reductive Elimination Reactions from Au(III) Centers.

(A) C(aryl)–C(aryl) reductive elimination from an Au(III) complex: (i) exceptionally fast C(aryl)–C(aryl) reductive elimination; and (ii) C(aryl)–C(aryl) reductive elimination to form fluorinated birayls. (B) C(aryl)–P reductive elimination from an Au(III) complex. (C) C(aryl)–P and C(aryl)–N reductive elimination from cyclometalated Au(III) complexes. (D) Supramolecule-facilitated reductive elimination from an Au(III) complex. (E) C(alkyl)–CF₃ reductive elimination via a fluoride-rebound mechanism.