Organogold chemistry: II reactions

Parish, R. V.

doi:10.1007/bf03214757

Cited by 20 publications

(27 citation statements)

References 48 publications

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“…For gold(III), reductive elimination of two ligands in a cis relationship happens quite readily to give gold(I) species. 30 There is no evidence in the elimination reactions that organic radicals are involved. 30 The oxidation state of gold is usually unchanged during the catalytic cycle as it has proven difficult to re-oxidise gold.…”

Section: Redox-chemistry Of Goldmentioning

confidence: 99%

“…30 There is no evidence in the elimination reactions that organic radicals are involved. 30 The oxidation state of gold is usually unchanged during the catalytic cycle as it has proven difficult to re-oxidise gold. 25 There are a few examples of catalytic reactions where gold(I)/gold(III) redox cycles are suggested, [31][32][33][34] but the reports are still rather few and whether or not trace amounts of palladium were present in some cases has been debated.…”

Section: Redox-chemistry Of Goldmentioning

confidence: 99%

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Versatile Methods for Preparation of New Cyclometalated Gold(III) Complexes

et al. 2012

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The interest in organogold compounds continues to grow. Gold(III) complexes are being investigated as catalysts for organic transformations as well as tested as potential anti-cancer drugs. Despite this wide-ranging interest in the properties of such complexes, the synthetic methods for preparing them are underdeveloped. Thus, Chapter 2 discusses the synthesis of cyclometalated gold(III) complexes bearing the C-N chelating ligand 2-(p-tolyl)pyridine (tpy). Monoalkylation andarylation were possible by use of Grignard reagents, whereas alkyl and aryl lithium reagents gave the dialkylated and diarylated gold(III) complexes. By a combination of the two alkylation procedures, mixed alkyl/aryl complexes of the type AuMePh(tpy) were obtained and both isomers were available. Chapter 3 discusses the reactivity of the cyclometalated gold(III) complexes towards different gases such as carbon monoxide and oxygen. Most of the cyclometalated gold(III) complexes prepared react with acids. The monoalkylated and-arylated complexes of the type AuBrR(tpy) (R = Me, Et, CHCH 2 , CCH, Ph) react with silver(I) salts to give a potential open coordination site at gold(III). Ethylene formally inserts into the Au-O bond trans to nitrogen in the chelating C-N ligand of the complex Au(OCOCF 3) 2 (tpy) (62) in trifluoroacetic acid or dichloromethane, to yield Au(CH 2 CH 2 OCOCF 3)(OCOCF 3)(tpy) (94). In trifluoroethanol, a slightly different complex resulted due to nucleophilic attack by trifluoroethanol rather than trifluoroacetate, Au(CH 2 CH 2 OCH 2 CF 3)(OCOCF 3)(tpy) (95). The mechanism of the insertion was investigated experimentally as well as computationally and the results are discussed in Chapter 4. The formal insertion takes place with alkenes other than ethylene, and alkynes react too. A key step in the catalytic reactions involving gold(III) is assumed to be the coordination of a CC multiple bond to the gold centre. Various catalytic cycles involving a gold(III) π-complex have been proposed. However, gold(III) alkene, alkyne, allene, or arene complexes have until recently not been conclusively detected and characterised. Chapter 5 discusses the first, and thus far only, crystallographically characterised gold(III) alkene complex, Au(cod)Me 2 BArF (133-BArF, BArF = tetrakis[3,5-bis(trifluoromethyl)phenyl]borate, cod = 1,5-cyclooctadiene).

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Section: Redox-chemistry Of Goldmentioning

confidence: 99%

Section: Redox-chemistry Of Goldmentioning

confidence: 99%

Versatile Methods for Preparation of New Cyclometalated Gold(III) Complexes

et al. 2012

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Section: Discussionmentioning

confidence: 99%

“…4) Organogold intermediates undergo fast protodemetallation. 5) Due to the easy reduction and the difficult oxidation of gold, a cross-coupling chemistry seems to be difficult to reach due to the necessary change of oxidation states and most reactions presented here probably do not go along with oxidation or reduction of the catalytically active gold species in the catalytic cycle (94,95,96,97 Figure 51.One can clearly see two major 'peaks', one was probably initiated in 1986 by Ito and Hayashi's discovery of the asymmetric aldol reaction, the second can be related to both Teles' (69,70) 1998 finding of highly active catalysts for the addition of heteronucleophiles to alkynes and the Dyker (98) 'Highlight' paper from 2000 on the C-C-bond formation reactions developed by Hashmi et al in 2000 (34,40).I am confident, that these developments will accelerate in the near future, and that most people working in the field of homogeneous transition metal catalysis will also give gold a chance on a regular basis. …”

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Homogeneous catalysis by gold

2004

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A comprehensive overview in the field of homogeneous catalysis by gold is given and the basic principles are discussed. It is also highlighted where homogeneous gold catalysts are already superior to other catalysts and where future possibilities for advantageous use of homogeneous gold catalysts exist.For a long time, gold was considered to possess only low catalytic activity ("catalytically dead") and therefore only its stoichiometric co-ordination and organo-metallic chemistry was investigated intensively. Even in the 19th century it was quite popular to characterize precious alkaloid bases after their troublesome isolation from natural sources as tetrachloroaurates (1,2).Since then, a change of paradigm has taken place (3). Among the numerous applications for gold, its use as a catalyst, albeit not yet consuming large amounts of this metal, has attracted much attention. Overall, in the chemical databases ca. 230,000 papers on gold can be found, of which about 9,000 deal with gold catalysis (from the SciFinder database in October 2003). The field of gold catalysis is dominated by heterogeneous catalysts, while homogeneous catalysts still represent the much smaller part (about 100 hits). Still, a significant amount of different homogeneous gold-catalysed reactions is known and basic principles can be deduced from them.In this article only publications in which gold is unambiguously the site of the catalysis reaction will be covered. This, for example, excludes the use of some mixed metal clusters and mixed metal colloids. BackgroundHomogeneous catalysis includes all reactions in which the substrate(s) and the catalyst are in the same state. As there exists only a limited number of highly volatile gold compounds, most of these reactions are conducted in the liquid phase with either liquid or dissolved substrate(s) and a dissolved catalyst. Homogeneous catalysis in the solid state, a part of the solvent-free reactions (4) that are nowadays quite popular in the field of green chemistry, has not been explored with gold yet (with the exception shown in Figure 31)! In this context, the non-toxicity of gold, which helps to avoid any environmental problems, is also of importance.The catalyst itself promotes a chemical reaction, a process in which chemical compounds (the substrates) are converted to other chemical compounds (the products), to proceed under milder reaction conditions (lower temperatures, lower pressure, lower concentrations of the substrates, higher or different selectivity). As the catalyst is not consumed, a catalytic amount is sufficient -but this is often a matter of debate: for some scientists 20 mol% of 'catalyst' are still catalytic, while others may consider this to be a substoichiometric reaction and accept only 0.001 mol% or less as catalytic.Two motives drive the desire to produce a chemical reaction: The use of gold as a catalyst is desirable when it has a similar activity as for a more expensive catalyst, when it shows a higher activity or a higher selectivity than less expensive catalysts...

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“…Trialkyl-and triphenylphosphines are good stabilizers of trimethylgold(III) [90]. ; some of those derivatives are considered as promising precursors for MOCVD of film materials [93].…”

Section: Gold(iii) Compounds Stabilized By р Atomsmentioning

confidence: 99%