title: Phosphinines versus mesoionic carbenes: a comparison of structurally related ligands in Au(i)-catalysis.
abstract: Gold(i) complexes based on a 2,4,6-triarylphosphinine and a mesoionic carbene derivative have been prepared and characterized crystallographically. Although structurally related, both heterocycles differ significantly in their donor/acceptor properties. These opposed electronic characteristics have been exploited in Au(i)-catalyzed cycloisomerization reactions. For the conversion of the standard substrate dimethyl 2-(3-methylbut-2-enyl)-2-(prop-2-ynyl)malonate the results obtained for both Au-catalysts were found to be very similar and comparable to the ones reported in the literature for other carbene- or phosphorus(iii)-based Au(i)-complexes. In contrast, a clear difference between the catalytic systems was found for the cycloisomerization of the more challenging substrate N-2-propyn-1-ylbenzamide. A combination of the phosphinine-based complex and [AgSbF6] or [Cu(OTf)2] leads to a catalytic species, which is more active than the mesoionic carbene-based coordination compound. We attribute these differences to the stronger π-accepting ability of phosphinines in comparison to mesoionic carbenes. The here presented results show for the first time that phosphinines can be used efficiently as π-accepting ligands in Au(i)-catalyzed cycloisomerization reactions.
authors.affiliation: Institut für Chemie und Biochemie, Freie Universität Berlin, Fabeckstr. 34/36, 14195 Berlin, Germany. Biprajit.Sarkar@fu-berlin.de c.mueller@fu-berlin.de.
authors.forename: Massimo
authors.initials: M
authors.lastname: Rigo
authors.affiliation: Institut für Chemie und Biochemie, Freie Universität Berlin, Fabeckstr. 34/36, 14195 Berlin, Germany. Biprajit.Sarkar@fu-berlin.de c.mueller@fu-berlin.de.
authors.forename: Lara
authors.initials: L
authors.lastname: Hettmanczyk
authors.affiliation: EaStCHEM, School of Chemistry, University of St Andrews, North Haugh, St Andrews, KY16 9ST, UK.
authors.forename: Frank J L
authors.identifier: http://orcid.org/0000-0001-8587-8127
authors.initials: FJ
authors.lastname: Heutz
authors.affiliation: Institut für Chemie und Biochemie, Freie Universität Berlin, Fabeckstr. 34/36, 14195 Berlin, Germany. Biprajit.Sarkar@fu-berlin.de c.mueller@fu-berlin.de.
authors.forename: Stephan
authors.initials: S
authors.lastname: Hohloch
authors.affiliation: Bijvoet Center for Biomolecular Research, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands.
authors.forename: Martin
authors.initials: M
authors.lastname: Lutz
authors.affiliation: Institut für Chemie und Biochemie, Freie Universität Berlin, Fabeckstr. 34/36, 14195 Berlin, Germany. Biprajit.Sarkar@fu-berlin.de c.mueller@fu-berlin.de.
authors.forename: Biprajit
authors.initials: B
authors.lastname: Sarkar
authors.affiliation: Institut für Chemie und Biochemie, Freie Universität Berlin, Fabeckstr. 34/36, 14195 Berlin, Germany. Biprajit.Sarkar@fu-berlin.de c.mueller@fu-berlin.de.
authors.forename: Christian
authors.initials: C
authors.lastname: Müller