UvA-DARE (Digital Academic Repository) Dinuclear Gold Complexes Supported by Wide Bite Angle Diphosphines for Preorganization-Induced Selective Dual-Gold Catalysis Lankelma, M.; Vreeken, V.; Siegler, M.A.; van der Vlugt, J.I. DOI 10.3390/inorganics7030028 Publication date 2019 Document Version Final published version Published in Inorganics License CC BY Link to publication Citation for published version (APA): Lankelma, M., Vreeken, V., Siegler, M. A., & van der Vlugt, J. I. (2019). Dinuclear Gold Complexes Supported by Wide Bite Angle Diphosphines for Preorganization-Induced Selective Dual-Gold Catalysis. Inorganics, 7(3), [28]. https://doi.org/10.3390/inorganics7030028 General rights It is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulations If you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: https://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. UvA-DARE is a service provided by the library of the University of Amsterdam (https://dare.uva.nl) Download date:02 Oct 2021 inorganics Article Dinuclear Gold Complexes Supported by Wide Bite Angle Diphosphines for Preorganization-Induced Selective Dual-Gold Catalysis Marianne Lankelma 1, Vincent Vreeken 1, Maxime A. Siegler 2 and Jarl Ivar van der Vlugt 1,* 1 Homogeneous, Supramolecular, and Bio-inspired Catalysis, van ’t Hoff Institute for Molecular Sciences, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands; [email protected] (M.L.); [email protected] (V.V.) 2 Small Molecule X-ray Laboratory, Department of Chemistry, Johns Hopkins University, Baltimore, MD 21218, USA; [email protected] * Correspondence: [email protected]; Tel.: +31-20-5256459 Received: 29 January 2019; Accepted: 20 February 2019; Published: 26 February 2019 Abstract: The synthesis, reactivity, and potential of well-defined dinuclear gold complexes as precursors for dual-gold catalysis is explored. Using the preorganizing abilities of well-known wide bite angle diphosphine ligands, DBFPhos and DPEPhos, dinuclear Au(I)–Au(I) complexes 1 and 2 are used as precursors to form well-defined monocationic species with either a chlorido- or acetylido-ligand bridging the two gold centers. These compounds are active catalysts for the dual-gold heterocycloaddition of a urea-functionalized alkyne, and the preorganization of both Au-centers affords efficient σ,π-activation of the substrate, even at high dilution, significantly outperforming benchmark mononuclear catalysts. Keywords: dinuclear gold complex; wide bite-angle diphosphine ligand; dual-gold catalysis; bridging acetylide; σ,π-activation 1. Introduction Recently, the catalytic activation of substrates using two gold centers has proven to be a valuable strategy for a wide range of transformations in the broader context of gold-mediated catalysis [1–14]. Commonly, mono-gold catalysis relies on π-activation of a substrate (e.g., an alkene) by a cationic Au(I) center. Dual-gold catalysis, on the other hand, can lead to both σ- and π-activation (either of the same functional group within a substrate or of two separate functional groups) by two Au centers. The proximity of both Au-centers has occasionally been credited to enhance reactivity [15–17]. The prevailing strategy utilizes mononuclear Au(I) complexes to induce this mode of activation (Scheme1)[ 18]. However, this approach offers no handles to induce preorganization of both Au-centers to specifically target well-defined σ,π-activation of, for example, C–C multiple bonds whilst avoiding π- or simultaneous σ- and π-coordination (one mode per Au-center), nor does it provide any control over the selective binding of bifunctional substrates (e.g., for heterocyclizations). We have recently reported the catalytic competence of well-defined dinuclear σ,π-alkynide complexes in dual-gold catalysis, highlighting the importance of two preorganized Au centers with respect to regioselectivity and activity for intramolecular hydroamination [19,20]. This was achieved using the ditopic tridentate ligand PNHPiPr (2,20-bis(diisopropylphosphino)-4,40-ditolylamine) (Figure1). However, under certain (catalytically relevant) conditions, the redox-active nature of this scaffold induced significant structural rearrangement of the ligand backbone, giving rise to a carbazolyl-based derivative. In order to eliminate such ligand-centered chemistry leading to structural reorganization, and to exploit more readily available diphosphine ligands, we investigated wide bite angle diphosphine ligands with Inorganics 2019, 7, 28; doi:10.3390/inorganics7030028 www.mdpi.com/journal/inorganics Inorganics 2019, 7, 28 2 of 13 Inorganics 2018, 6, x 2 of 13 ether backbonesInorganics [21 2018–,29 6, x]. Basic coordination chemistry of these potentially dinucleating2 of 13 ligands diphosphine ligands with ether backbones [21–29]. Basic coordination chemistry of these potentially towarddinucleating golddiphosphine has alreadyligands ligands beentoward with established ethergold backbones has byalready [21–29]. several Basicbeen groups coordination established [30– chemistry32 ].by Furthermore, several of these potentiallygroups Koshevoy [30–32]. et al. dinucleating ligands toward gold has already been established by several groups [30–32]. investigatedFurthermore, the formation Koshevoy and et al. photochemical investigated the properties formation of and bis-gold photochemical complexes properties with the of related bis-gold ligand Furthermore, Koshevoy et al. investigated the formation and photochemical properties of bis-gold Xantphoscomplexes [33complexes–38 with]. the with related the related ligand ligand Xantphos Xantphos [33–38]. [33–38]. redox-activeredox-active N reactive H N reactive P H P P P highly selective PreviousP work P P+ P [Au] Au highlydual-gold selective Previous work [Au]+ Au dual-goldcatalysis R catalysis σ, π O R P P σ, π O Current work P P Figure 1. Left:Figure Strategy 1. Left: for Strategy the preorganization for the preorganization of two gold-centersof two gold-centers for σ for–π -coordinationσ–π-coordination ofofhydrocarbon Current work π-systems usinghydrocarbon a diphosphine π-systems using platform. a diphosphine Right: platform. previous Right: and previous current and work current on work bis-gold on bis-gold chemistry with chemistry with specific diphosphine ligands. specificFigure diphosphine 1. Left: Strategy ligands. for the preorganization of two gold-centers for σ–π-coordination of hydrocarbonWe herein π-systems report using on the a formation diphosphine of μ -chloridoplatform. and Right: σ,π-alkynide previous derivatives and current of workAu2Cl on2(κ2 bis-gold-P;P- Wechemistry hereinDBFPhos) with report and specific Au2 onCl 2diphosphine(κ2 the-P;P-DPEPhos) formation ligands. and catalytic of µ activity-chlorido of these and well-definedσ,π-alkynide dinuclear species derivatives of 2 vs. mononuclear benchmarks in the intramolecular2 hydroamidation of functionalized amido-alkenes. Au2Cl2(κ -P;P-DBFPhos) and Au2Cl2(κ -P;P-DPEPhos) and catalytic activity of these well-defined This study emphasizes the positive effect of preorganization of two gold centers for reactions that We herein report on the formation of μ-chlorido and σ,π-alkynide derivatives of Au2Cl2(κ2-P;P- dinuclear speciesproceed vs. via mononuclear simultaneous σ-benchmarks and π-activation in of the a carbon-based intramolecular π-system hydroamidation in a substrate. This ofeffect functionalized DBFPhos) and Au2Cl2(κ2-P;P-DPEPhos) and catalytic activity of these well-defined dinuclear species amido-alkenes.is illustrated This study via a dilution emphasizes study with the mono- positive and di-nuclear effect ofcatalysts. preorganization of two gold centers for vs. mononuclear benchmarks in the intramolecular hydroamidation of functionalized amido-alkenes. reactions that proceed via simultaneous σ- and π-activation of a carbon-based π-system in a substrate. This study2. Results emphasizes and Discussion the positive effect of preorganization of two gold centers for reactions that This effect is illustrated via a dilution study with mono- and di-nuclear catalysts. proceed via simultaneousThe straightforward σ- and reaction π-activation of L1 (DBFPhos) of a carbon-basedand L2 (DPEPhos) π -systemwith AuCl(SMe in a substrate.2) in a 1:2 ratio This effect is illustratedprovided via awhite dilution solids study 1 (31P NMR:with δmono- 23.3) and and 2 (di-nuclear31P NMR: δ 21.6).catalysts. The respective 1H NMR spectra 2. Results andwere Discussion suggestive of C2 symmetric species (Scheme 1). Single crystals suitable for X-ray structure 2. Resultsdetermination and Discussion of 2 were obtained by slow vapor diffusion of acetone into a solution of 2 in CHCl3 The straightforward(Figure 2), while for reaction 1 only a ofconnectivityL1 (DBFPhos) plot could and be reliablyL2 (DPEPhos) obtained (from with single AuCl(SMe crystals grown2) in a 1:2 ratio 31 31 1 10 providedThe whitefrom straightforward solidsCH2Cl2–pentane;1