Gold compounds can surpass nickel and palladium-based catalysts in common reactions + often demonstrate novel types of reactivity compared to well-established catalysts. This allowed chemists to discover new chemical reactions and predetermined a fascinating boom in gold catalysis that we have observed in the recent years.
Professor Ananikov’s team introduced gold into well-known catalytic system which led to dramatic change of the reactivity and furnished the formation of novel gold-containing complexes. They appeared to be air stable and were isolated in the individual state. A single crystal Xray diffraction study ascertained the existence of a unique structural motif in the molecule, which cannot be explained within a conventional mechanistic framework.
The study used both theoretical and experimental approaches. Labeling of the reagents allowed observation of molecular reorganizations. Variation of reaction conditions helped to estimate key factors governing the transformation. Computational study of the reaction provided models of certain intermediate steps, which were invisible for experimental investigation. The theoretical data was in agreement with the experiment, and they propose a reaction mechanism in which a molecule of acetic acid serves as a proton shuttle, transferring H atom between reaction centers.
The early belief in gold inactivity towards chemical transformations resulted in the fact that gold-related organometallic chemistry was developed significantly later than other coinage metals (like silver, nickel or copper). Today, the goal is to “introduce gold catalysis as a valuable practical tool in fine organic chemistry, competitive with other transition metal catalysts”, says Prof. Valentine P. Ananikov.
http://phys.org/news/2015-07-acetic-acid-proton-shuttle-gold.htmljCp
Carboxylic group-assisted proton transfer from acetic acid to an alkyne molecule is the key step in the unique gold-mediated alkyne transformation that leads to the formation of gem-disubstituted vinyl gold complexes. The structures of the complexes were established using NMR spectroscopy (in solution) and X-ray diffraction (in the solid state). ESI-MS study of the reaction mixture revealed multiple gold-containing complexes and clusters. Investigation of the MS2 fragmentation patterns of the selected ions suggested the involvement of gold acetylides in the transformation. Further treatment of the complexes with protic acid led to the discovery of a novel route for the gold-mediated alkyne hydrothiolation.
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