The conversion of a variety of well‐known test reactions, representing the key reactivity patterns of gold catalysis, were analyzed by GC and 1H NMR. The study is focused on establishing of a strategical approach for the consideration of ligand influence and counter anion influence during the catalyst optimization including an industrial perspective. The study shows a dominance of the counter anion, a dominance which up to now has been neglected in most of the routine screenings. In addition, a drastic substrate‐dependency became obvious, even a marginal variation of the substrate already could strongly effect the catalytic activity and change the optimal counter anion or ligand. Based on the collected data a strategic concept for an efficient screening for a specific substrate is introduced, this concept can serve as an important guideline for catalyst optimization in homogeneous gold catalysis.magnified image

A comparison of versatile counter anions was investigated by means of a variety of well‐known test reactions representing the key reactivity patterns of homogeneous gold catalysis, the catalytic activity was monitored by GC and 1H NMR. As previously reported, the counter anion influence is usually more pronounced than the corresponding ligand effect. Due to this, the study is focused on the investigation of counter anions so far not included from investigation of homogeneous gold‐catalyzed reactions. The examinations using so far neglected counter anions (BArF4)−, [B(C6F5)4]−, [Al(OC(CF3)3)4]− and [B(C6F5)3(OAcF)]− showed surpassing or at least similar catalytic activities as the commonly used counter anions. The expanded use of counter anions can occupy an important role in future concerning catalyst optimization in gold catalysis.magnified image

We have probed for reaction intermediates involved in the dual-gold-catalyzed activation of a conjugated 1,5-diyne substrate and its further coupling to benzene in the liquid phase. This was done by sampling the reaction mixture by electrospray ionization followed by high-resolution ion mobility mass spectrometryunder conditions allowing for the resolution of structural isomers differing in their collision cross sections by less than 0.5%. For the cationic mass corresponding to catalyst + diyne (activation stage) we resolve four isomers. At the mass corresponding to catalyst + diyne + benzene, two isomers are observed. By comparing the experimentally obtained cross sections to those inferred for model structures derived from density functional computations, we find our measurements to be consistent with the proposed solution mechanism. This constitutes the first direct observation of intermediates in dual gold catalysis and supports the previous inference that the mechanism involves cooperative interactions between two gold centers.

The gold‐catalyzed facile synthesis of U‐shaped and S‐shaped bispentalenes is described from easily available tetra(arylethynyl)‐benzenes and ‐naphthalenes. The optoelectronic and transistor properties were also investigated. The selectivity between the U‐shaped and S‐shaped bispentalene isomers can be tuned by the bulkiness of the ligand and the substrates. The S‐shaped naphthalene‐based bispentalene shows a one‐dimensional face‐to‐face packing pattern in solid state and a good hole mobility, indicating that the S‐shaped bispentalene core is highly suitable for transistor applications. The gold‐catalyzed annulation of tetraynes provides a useful protocol in the synthesis of bispentalenes for organic semiconductors.

The reaction of a platinum acetylide derived from a 1,2‐dialkynylarene with a phosphanegold(I) species delivered a σ‐platinum‐π‐gold coordination to the same triple bond of the organic substrate. Cyclopentadienyl‐di(phosphanyl)ruthenium(II) acetylides of the same substrate type gave vinylgold(I)‐vinylideneruthenium(II) complexes in similar reactions. A switch to the corresponding cyclopentadienyl‐di(carbonyl)ruthenium(II) species with a phenyl group on the second alkyne provided vinylruthenium(II) complexes in which the ruthenium was still bound to the same carbon as in the starting material, with a tert‐butyl group on the second alkyne vinylruthenium(II) complexes in which the ruthenium has migrated to another carbon, were obtained. This reactivity mimics the initial steps suggested for dual gold catalysis with these substrates and thus for the first time experimentally confirms the organometallic reactivity patterns proposed for the single steps.magnified image