title: Direct and Autocatalytic Reductive Elimination from Gold Complexes ([(Ph3P)Au(Ar)(CF3)(X)], X=F, Cl, Br, I): The Key Role of Halide Ligands.
abstract: Kinetic and thermodynamic preferences for the reductive elimination of Caryl-CF3, Caryl-X, Caryl-P, and CF3-X bonds and competitive phosphine dissociation from a series of AuIIIcomplexes [(Ph3P)Au(Ar)(CF3)(X)] (1X; Ar=4-Me-C6H4; X=F, Cl, Br, I) are studied computationally. Kinetically, the most favorable pathways were found to consist of an initial phosphine dissociation from complex 1X, which furnished the respective three-coordinate AuIIIcomplexes [Au(Ar)(CF3)(X)] (2X). The computed enthalpy barriers for various reductive elimination reactions from complex 2Xby a direct (or uncatalyzed) mechanism showed that Caryl-CF3bond formation was the most favorable fate for any X group. When the direct elimination was compared with an autocatalytic mechanism that proceeded through the formation of a mixed-valent binuclear AuIII-AuIintermediate, the preference for the formation of a Caryl-CF3bond is dependent on the nature of the bridging halide atom and follows the order F>Cl>Br>I. Concomitantly, the selectivity for the formation of Caryl-X bonds for various X atoms follows the opposite trend. The preference for the direct and autocatalytic processes is controlled entirely by the nature of the halide ligand. The predicted mechanisms and product selectivity trends for various halides show excellent agreement with recent experimental observation. The selectivity of various reductive elimination pathways was rationalized by using molecular orbital theory and distortion-interaction model analyses. Attractive interactions between the AuIcomplex and complex 2Xwere found to reduce the activation barrier for Caryl-X elimination and critically control the selectivity of the product formation.
authors.affiliation: Department of Spectroscopy, Indian Association for the Cultivation of Science, Jadavpur, 700032, West Bengal, India.
authors.forename: Rameswar
authors.initials: R
authors.lastname: Bhattacharjee
authors.affiliation: Department of Spectroscopy, Indian Association for the Cultivation of Science, Jadavpur, 700032, West Bengal, India.|Department of Chemistry, University at Buffalo, The State University of New York, Buffalo, NY, 14260-3000, USA.
authors.forename: A
authors.initials: A
authors.lastname: Nijamudheen
authors.affiliation: Department of Spectroscopy, Indian Association for the Cultivation of Science, Jadavpur, 700032, West Bengal, India.
authors.forename: Ayan
authors.initials: A
authors.lastname: Datta
keywords: autocatalysis; computational chemistry; distortion-interaction model; gold catalysis; reductive elimination