title: Direct observation of two-electron Ag(I)/Ag(III) redox cycles in coupling catalysis.
abstract: Silver is extensively used in homogeneous catalysis for organic synthesis owing to its Lewis acidity, and as a powerful one-electron oxidant. However, two-electron redox catalytic cycles, which are most common in noble metal organometallic reactivity, have never been considered. Here we show that a Ag(I)/Ag(III) catalytic cycle is operative in model C-O and C-C cross-coupling reactions. An aryl-Ag(III) species is unequivocally identified as an intermediate in the catalytic cycle and we provide direct evidence of aryl halide oxidative addition and C-N, C-O, C-S, C-C and C-halide bond-forming reductive elimination steps at monometallic silver centres. We anticipate our study as the starting point for expanding Ag(I)/Ag(III) redox chemistry into new methodologies for organic synthesis, resembling well-known copper or palladium cross-coupling catalysis. Furthermore, findings described herein provide unique fundamental mechanistic understanding on Ag-catalysed cross-coupling reactions and dismiss the generally accepted conception that silver redox chemistry can only arise from one-electron processes.
authors.affiliation: Institut de Química Computacional i Catàlisi (IQCC) and Departament de Química, Universitat de Girona, Campus Montilivi, Girona E-17071, Catalonia, Spain.
authors.forename: Marc
authors.initials: M
authors.lastname: Font
authors.affiliation: Institut de Química Computacional i Catàlisi (IQCC) and Departament de Química, Universitat de Girona, Campus Montilivi, Girona E-17071, Catalonia, Spain.
authors.forename: Ferran
authors.initials: F
authors.lastname: Acuña-Parés
authors.affiliation: Servei de RMN, Facultat de Ciències, Universitat Autònoma de Barcelona, Campus UAB, Bellaterra E-08193, Catalonia, Spain.
authors.forename: Teodor
authors.initials: T
authors.lastname: Parella
authors.affiliation: Institut de Química Computacional i Catàlisi (IQCC) and Departament de Química, Universitat de Girona, Campus Montilivi, Girona E-17071, Catalonia, Spain.
authors.forename: Jordi
authors.initials: J
authors.lastname: Serra
authors.affiliation: Institut de Química Computacional i Catàlisi (IQCC) and Departament de Química, Universitat de Girona, Campus Montilivi, Girona E-17071, Catalonia, Spain.
authors.forename: Josep M
authors.initials: JM
authors.lastname: Luis
authors.affiliation: Institut de Química Computacional i Catàlisi (IQCC) and Departament de Química, Universitat de Girona, Campus Montilivi, Girona E-17071, Catalonia, Spain.
authors.forename: Julio
authors.initials: J
authors.lastname: Lloret-Fillol
authors.affiliation: Institut de Química Computacional i Catàlisi (IQCC) and Departament de Química, Universitat de Girona, Campus Montilivi, Girona E-17071, Catalonia, Spain.
authors.forename: Miquel
authors.initials: M
authors.lastname: Costas
authors.affiliation: Institut de Química Computacional i Catàlisi (IQCC) and Departament de Química, Universitat de Girona, Campus Montilivi, Girona E-17071, Catalonia, Spain.
authors.forename: Xavi
authors.initials: X
authors.lastname: Ribas