Gold(ii) in redox-switchable gold(i) catalysis

Abstract

Gold(ii) species catalyse the cyclisation of N(2-propyn-1-yl)benzamide to 2-phenyl-5-vinylidene-2-oxazoline without halide abstraction while the neutral gold(i) complex is inactive indicating a gold(ii/i) redox-switch.

Triple the fun: tris(ferrocenyl)arene-based gold(i) complexes for redox-switchable catalysis

“…[99][100][101][102][103][104] The groups of Sarkar and Heinze, among others, have established the transformation of 5 to 6 as a platform to perform and study RSC using gold(I) catalysts. [105][106][107][108][109] Rendering the gold(I) centres reversibly more Lewis-acidic and hence more catalytically active 110 through oxidation of a connected ferrocenyl moiety is one way of obviating the sometimes problematic use of silver salts for activation of gold(I) precatalysts by halide abstraction and enables temporal control over the activity of the catalyst. [111][112][113][114][115] Since we aimed for a detailed understanding of the switching process, the reaction was performed on the NMR scale in CD 2 Cl 2 , allowing for a time-resolved study of the reaction through protons H o (reaction involving oxidised species) and H m (reactions not involving oxidised species) of oxazoline 6 ( Fig.…”

“…À and SbCl 6 À have been shown to form tight ion pairs with ferrocenium, 105,126 and anion effects in general have been found crucial for the understanding and tailoring of gold catalysts. 127 Aer the reaction shown in Fig.…”

Coordination Booster‐Catalyst Assembly: Remote Osmium Outperforming Ruthenium in Boosting Catalytic Activity

“…The present study demanded as ystematic designo ft he Con-Cat assemblies to probe the boosting effect of "Os II (terpy) 2 "i n comparison to "Ru II (terpy) 2 "i nt he selected oxidative catalysis. Therefore, with this idea, the (Con-Cat)a ssemblies-[Ru II (terpy) 2 -Ru II (NHC)(p-cymene)Cl](PF 6 ) 3 (Ru Con -Ru Cat )a nd [Os II (terpy) 2 -Ru II (NHC)(p-cymene)Cl](PF 6 ) 3 (Os Con -Ru Cat ), and the (Cat-Con-Cat)a ssemblies-[Ru II (NHC)(p-cymene)Cl-Ru II (terpy) 2 -Ru II (NHC)(p-cymene)Cl](PF 6 ) 4 (Ru cat -Ru Con -Ru Cat )a nd [Ru II (NHC)(p-cymene)Cl-Os II (terpy) 2 -Ru II (NHC)(p-cymene)Cl](PF 6 ) 4 (Ru cat -Os Con -Ru Cat )w ere employed in this study,i nl ine with our preliminaryr eport on boosting effect of (Ru Con -Ru Cat )i nc omparisont ot he activity of the model catalyst mod Ru cat (Figure 2). [5a] The new systems (Os Con -Ru Cat ), (Ru cat -Ru Con -Ru Cat ), and (Ru cat -Os Con -Ru Cat )w ere synthesized in accordance with the procedure used for (Ru Con -Ru Cat )a nd characterizedf ully by 1 H, 13 C{ 1 H}, and 2D NMR spectroscopic, and high-resolution electron-spray ionizationm ass spectrometric (HR-ESIMS) techniques (for details, see Supporting Information).…”

“…[1] In synthetic designer catalyst systems, Consh ave not only been used as structural changeinduced effectors but also as electronic change-based effectors to the Cats. Important examples of Consa cting as effectors to the Catsv ia stereo-electronic perturbations include a) chromophores for light-induced control, [2] b) redox-responsive center for electrochemical control, [3] c) Lewis acidic moieties for electronic control, [4] and d) coordinationc omplexes for structural and/or electronic control [5] etc..R emarkable effects on the regulation of catalytic activity have been achieved through such approaches. This opens up the possibility of realizing andd evelopingn ew and unique Con-Cat assemblies ( Figure 1A).…”

The core of the matter – arene substitution determines the coordination and catalytic behaviour of tris(1-phosphanyl-1′-ferrocenylene)arene gold(i) complexes

“…As a suitable model reaction for testing the previously presented mono-and trinuclear complexes in RSC, the ringclosing isomerisation of propargylic amide 2 to oxazoline 3a (Scheme 1) 18,[123][124][125][126] was studied by time-resolved 1 H NMR spectroscopy vs. an internal standard (1,3,5-trimethoxybenzene) in CD 2 Cl 2 . While trinuclear chloridogold(I) complexes of 1a-c exclusively yielded 3a with an exocyclic methylene group, 36 other (redox-switchable) gold(I/III) catalysts are known to also catalyse the aromatisation of 3a to oxazole 3b in a subsequent step.…”