Gold complexes olefins

Hydroamination of olefins has received considerable attention this year as a route to functionalized piperidines and spiropiperidines, particularly in regard to the investigation of new catalysts. In the synthesis of spiro-piperidines, two new mild and more general intramolecular hydroamination protocols were developed this year. One protocol uses a cationic gold-phosphine complex (Au[P(fBu)2(o-biphenyl)]Cl) as the catalyst... 

The cationic dinuclear oxo-gold(m) complexes of substituted bipyridyls react with olefins to give the stable coordination compounds shown in Scheme 79. The reactions are often incomplete, produce many byproducts, and give low yields of the olefin complexes/... 

In the case of gold, also, the number of known, stable olefin complexes is very small. 

Kneen (4, 31) prepared a series of copper(I), silver(I) and gold(I) complexes containing olefinic tertiary phosphines and arsines for several reasons ... 

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). 

Several gold(I) olefin complexes have been prepared, although the exact constitution was often in some doubt. The first olefin complex was reported (73) in 1964, when white crystals were obtained from the reaction of cycloocta- 1,5-diene (cod) with AuCl or HAuC14. These products were believed to be a dimeric aurous complex [Au2Cl2(cod)]. Subsequent reports, however, showed that although gold(I) chloride reacted (74) to give... 

With monoolefins apparently simple complexes of the type [AuCI-(olefin)] were obtained (74-76), whereas di- and triolefins gave dimeric species. With norbornadiene both monomeric and dimeric compounds were isolated (74). A gold(I) complex was also obtained from the reaction of auric chloride with hexamethyl Dewarbenzene (77). 

Molecular weight and conductivity measurements on the simple gold(I) complexes [AuCl(olefin)] showed (5/) them to be monomeric and undissociated in solution. The mixed complexes, on the other hand, were found to be 1 1 electrolytes in polarizing solvents with AuClJ as anion and, presumably, a bis- or tris(olefin)gold(I) species as cation. Of the mixed valence complexes only [Au2Cl4(nbd)] was undissociated, due to the necessity to retain a linear, two-coordinate gold(I) center. 

Fig. 1. Structures of mixed gold(I)-gold(III) olefin complexes.

Subsequently, Hiittel and co-workers (303, 306, 307) have described a series of gold(I)-olefin complexes involving both cyclic and acyclic mono- and oligoolefins (Table VI). The 1 1 monoolefin complexes, prepared in almost quantitative yield by reaction of excess olefin with AuCl in ether, are monomolecular and are obtained as colorless crystals. The cyclic olefins, which react as well with aqueous HAUCI4 or NaAuC, form complexes which are more stable than those of the corresponding straight-chain olefins. Formation of the complex results in a low infrared frequency shift in the C=C stretching vibration of 115 cm for the... 

Organogold compounds.34 Alkyl derivatives of gold were among the first organometallic compounds of transition metals to be prepared. Both gold(i) and gold(m) compounds with cr-bonds to carbon, as well as olefin complexes, are known. 

Olefin complexes of gold(I) can be prepared either by the reaction of tetrachloroau-ric acid with the olefin or directly from the olefin and gold(l) hahde 3 i5 While such species usually have poor stability and decompose in solution at room temperature, the cis-cyclooctene and norbornene complexes of AuCl, obtained from the reaction of [AuCl(CO)] with the corresponding olefin by a CO displacement reaction, have been found to be less prone to decomposition . An (olefin)gold(l) complex featuring a tetracoordinate environment for the gold centre bonded to the olefin has recently been obtained according to the procedure shown in equation 87 . 

Starting from tetrahydrocyclopenta[f)]furan-2-one 342, enyne 343, the substrate for the domino reaction, was prepared in 12 steps and with an overall yield of 45%. Exposure of 343 to the electron-rich gold(I) complex (t-Bu)2P(o-biphenyl)AuCl at room temperature afforded cis-hydrindanone 344 in 78% yield as a single stereoisomer (Scheme 14.54). The postulated mechanism involved Au(I) activation of the alkyne to initiate the cationic olefin cyclization of 346 to give carbocation 347, which then underwent a pinacol rearrangement to the final product 344. An originally attempted Lewis acid-catalyzed domino Prins/pinacol rearrangement of... 

Copper and silver form olefin complexes only if the metal has +1 oxidation state. Gold, in addition to Au(I) compounds, also forms polynuclear coordination compounds containing Au(I) and Au(III) (Figures 6.19 and 6.20, Table 6.18). The IR,... 

Copper, silver, and gold form complexes with olefins of the following composition [CuX(olefin)] (X = C1, Br olefin = ethylene, propylene, butenes, COT, NBD, etc. dienes in these complexes are monodentate ligands), [Cu2X2(COD)2],... 

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