Gold complexes with alkenes

Fig. 2.12 Silver, gold and platinum complexes with monodentate NHC ligands as catalysts for the diboration of alkenes and alkynes...

Complexes of Alkenes, Alkynes, and Arenes with Gold Compounds 299... 

From the encouraging results obtained in the reactions of a series of gold(III) oxo complexes with olefins [56], Cinellu et al. tried to achieve the supposed oxametalla-cyclic intermediate, which had never been isolated before [25]. In the reaction of 8 and norbornene 56, if the - atoms were considered to be equivalents of coordinated water, and it was therefore possible to talk about the gold-catalyzed addition of water to an alkene. The metallaoxetane 58 was separated from the gold-alkene complex 57 and characterized by X-ray crystal structure analysis. The subsequent stoichiometric reaction yielded epoxide 59 (Scheme 8.5). 

Only one paper has reported on catalytic asymmetric hydrogenation. In this study by Corma et al., the neutral dimeric duphos-gold(I)complex 332 was used to catalyze the asymmetric hydrogenation of alkenes and imines. The use of the gold complex increased the enantioselectivity achieved with other platinum or iridium catalysts and activity was very high in the reaction tested [195] (Figure 8.5). 

Alkenylboron compounds cyclopropanations, 9, 181 haloetherification, 9, 182 hydrogenation and epoxidation, 9, 182 metal-catalyzed reactions, 9, 183 metallic reagent additions, 9, 182 via radical addition reactions, 9, 183 5-Alkenylboron compounds, cross-coupling reactions, 9, 208 Alkenyl complexes with cobalt, 7, 51 with copper, 2, 160, 2, 174 with Cp Re(CO) (alkene)3 , 5, 915-916 with dicarbonyl(cyclopentadienyl)hydridoirons, 6, 175 with gold, 2, 255... 

Bis(adamantylimido) compounds, with monomeric chromium(VI) complexes, 5, 348 Bis(alkene) complexes conjugated, Rh complexes, 7, 214 mononuclear Ru and Os compounds, 6, 401 -02 in Ru and Os half-sandwich rj6-arenes, 6, 538 with tungsten carbonyls and isocyanides, 5, 685 Bis(u-alkenylcyclopentadienyl) complexes, with Ti(II), 4, 254 Bis(alkoxide) nitrogen-donor complexes, with Zr(IV), 4, 805 Bis(alkoxide) titanium alkynes, in cross-coupling, 4, 276 Bis(alkoxo) complexes, with bis-Cp Ti(IV), 4, 588 Bis[alkoxy(alkylamino)carbene]gold complexes, preparation, 2, 288... 

Cyclohexyldienyl complexes, with Ti(IV), 4, 327 Cyclohexylisocyanides, with gold(I) halides, 2, 281 Cyclohexylphosphine, for semiconductor growth, 12, 9 Cyclohexyl selenides, preparation, 9, 480 Cyclohydrocarbonylation alkenes, 11, 515 alkynes, 11, 522 dienes, 11, 522 overview, 11, 511-555 for ring expansion, 11, 527 Cycloisomerizations, via silver catalysts, 9, 558 Cyclomanganation, product types, 5, 777-778 Cyclometallated azobenzenes, liquid crystals, 12, 251 Cyclometallated complexes for OLEDs... 

Alkenes act as nucleophiles with alkynes in the presence of gold catalysts. In the most simple version of the reaction, enynes are converted with gold complexes or salts, and in the absence of nucleophiles, into rearranged dienes, cyclopropanated carbocycles, and/or bicyclic cyclobutenes. Depending on the length of the tether and the nature of the substituents, the olefin attack to the alkyne occurs in an endo or an exo fashion (equation 33). Besides, substitution at the alkene plays an important role on the regioselectivity of the nucleophilic attack. ... 

Besides organocatalysts, metal complexes show catalytic activities in various types of [3+2]cycloaddition. Thus Ru complex 140 performs a role in the reaction of nitrile oxides with enals, and gold(l) benzoate complex of Cy-SEGPHOS is involved in the reaction of miinchnones with alkenes. "... 

Alkene and alkyne r-complexes see Alkene Complexes and Alkyne Complexes are known both for Au and Au. They are prepared at low temperature from AuCl or AuCls with an excess of the alkene or alkyne in the absence of any other potential donor molecules. The products, for example, of the types (MeCH=CHMe)AuCl and MeC=CMe-(AuCl3)2, are generally of low stability, and the complexation is reversible in a vacuum or on heating. Representative examples have recently been structurally characterized.Strained cyclic alkenes and alkynes give the most stable products. Multiple coordination of monoalkenes or of dialkenes (like butadiene) is known, but information about the products is limited. Alkene coordination to neutral gold atoms has been studied by matrix-isolation techniques at very low temperature. The adduct (C2H4)Au appears to be stable only below 40 K. 

Catalytic conversions of allenes are sometimes considered models for catalytic reactions of alkenes, even though allene reactivity is more closely comparable to that of alkynes rather than alkenes. The catalytic hydration of allenes was achieved by means of a cationic gold(I) complex with a carbene steering ligand, (IPr)AuCl/ AgOTf (5 mol%), in dioxane (rt, 4—9 h) in fair yield [180]. Attack of water is selective for the terminal carbons, whereas regioselectivity in nonsymmetric substrates is controlled by steric, electronic, and solvation factors. 

The intermolecular reaction of alkynes 11-16 with alkenes II-17 catalyzed by gold(I) leads to cyclobutenes II-18 with complete regio- and diastCTeoselectivity. Moderate to good yields are obtained when gold(I) complex 7 with a very bulky phosphine ligand is used (Scheme 3.10) [Ref. 192 in Chap. 1]. This transformation shows that [2-1-2] cycloaddition predominates in the reaction between alkynes and alkenes when the constraints imposed by the tethers are absent, like in the intermolecular process. 

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