C(sp²)–C(sp²) Reductive Elimination from Well-Defined Diarylgold(III) Complexes

Abstract

A series of well-defined phosphine-ligated diarylgold­(III) complexes cis-[Au­(L)­(ArF)­(Ar′)­(Cl)] were prepared, and detailed kinetics of the C­(sp2)–C­(sp2) reductive elimination from these complexes were studied. The mechanism of the reductive elimination from the complexes cis-[Au­(L)­(ArF)­(Ar′)­(Cl)] was further studied by theoretical calculations. The combination of experimental and theoretical results suggests that the biaryl reductive elimination from organogold­(III) complexes cis-[Au­(L)­(ArF)­(Ar′)­(Cl)] proceeds through a concerted biaryl-forming pathway from the four-coordinated Au­(III) metal center. These studies also disclose that the steric hindrance of the phosphine ligands plays a major role in promoting the biaryl-forming reductive elimination from diarylgold­(III) complexes cis-[Au­(L)­(ArF)­(Ar′)­(Cl)], while electronic properties of these ligands have a much smaller effect. Futhermore, it was found that the complexes with more weakly electron withdrawing aryl ligands undergo reductive elimination more quickly and the elimination rate is not sensitive to the polarity of the solvents.

Gold‐Catalyzed Cross‐Coupling Reactions: An Overview of Design Strategies, Mechanistic Studies, and Applications

“…[319] Experimental and DFT investigations unraveled concerted reductive elimination from the four-coordinate Au center.S teric controlo ft he reaction kinetics owing to the phosphine ligand size was more evident than that resulting from the electronic effects of the aryl ligand. [319] Experimental and DFT investigations unraveled concerted reductive elimination from the four-coordinate Au center.S teric controlo ft he reaction kinetics owing to the phosphine ligand size was more evident than that resulting from the electronic effects of the aryl ligand.…”

“…[326] The microenvironment within Ga 4 L 6 12À (L = N,N'-bis (2,3-dihydroxybenzoyl)-1,5-diaminonaphthalene) [327][328][329] can encapsulate the complex cis-Et 3 PAu(CH 3 ) 2 Ia nd activate the ethane elimination with ah alf-timeo fj ust 47 sc ompared with 45 days required for ethane elimination in its absence (Scheme 67). [319] (b) Concerted roomtemperature C(aryl)ÀC(CF 2 H) reductive elimination from four-coordinate Au III complexes. The study establishes that by successfully merging the organometal catalysts with the catalytic activity of the microenvironment,f aster and practical cross-coupling can be realized.…”

“…In ar ecent study,S hen et al elucidated the kinetics and mechanisms for the concerted C(sp 2 )ÀC(sp 2 )r eductive elimination from well-defined four-coordinate gold complexes cis-[Au(L)(Ar F )(Ar')(Cl)] (Scheme 66 a, Ar F = C 12 F 8 H, L = phosphine ligand). [319] Experimental and DFT investigations unraveled concerted reductive elimination from the four-coordinate Au center.S teric controlo ft he reaction kinetics owing to the phosphine ligand size was more evident than that resulting from the electronic effects of the aryl ligand. This may be because Ar F is already ah ighly electron-deficient coupling partner.T he electronic effects owing to the substitution of both aryl partners for ab iaryl coupling from Au are found to be additive from previous computational [309] and experimental [191] studies.…”

Reductive Elimination Leading to C−C Bond Formation in Gold(III) Complexes: A Mechanistic and Computational Study

“…[10,11] The nature of the species involved in catalysis is often speculative,b ecause the range of studies on well-definedc omplexesi ss of ar limited to specific alkyls or aryls and does not yet allow ag eneral picture to be drawn of the factors that favour reductive eliminations. [15] In all these cases eliminationw as thought to proceed from af our-coordinate phosphine complex. [12] More precise information aboutt he structure of species involved in reductive eliminations is availablef or phosphine complexes [(R 3 P)AuCl(R 1 )(R 2 )],w here R 1 = aryl and R 2 = either fluoroaryl or CF 3 .N evadoe tal.…”

“…[13,14] Variationso ft he phosphine ligand in similarc ross-coupling reactions of perfluoroaryls at 85-150 8Cs howedt hat the steric requirements of the phosphines seem to play al arger role than their electronic properties. [15] In all these cases eliminationw as thought to proceed from af our-coordinate phosphine complex.…”