Gold complexes azides

In an attempt to make the normal gold(I) azide, Rogers [208] reacted HAUCI4 and solid sodium azide in ether. The product resembled the properties of Curtius azidoaurate, but had the empirical composition NaiAuj. 43N9.. 05 Rogers considered the substance to be a new discrete phase [208], but it was more probably a mixture of Au(I) and Au(III) azido complexes [139]. 

Scheme 11 (a) A )i -Ti Ti -acetylide bimetallic Au catalyst (24) used in the azide-alkyne cycloaddition, (b) a gem-diaurated catalyst (25) used for the cycloaddition of dialkynes, and (c) a trimetallic gold complex (26) used in the cycloisomerisation of allenynes... 

The NHCs have been used as ligands of different metal catalysts (i.e. copper, nickel, gold, cobalt, palladium, rhodium) in a wide range of cycloaddition reactions such as [4-1-2] (see Section 5.6), [3h-2], [2h-2h-2] and others. These NHC-metal catalysts have allowed reactions to occur at lower temperature and pressure. Furthermore, some NHC-TM catalysts even promote previously unknown reactions. One of the most popular reactions to generate 1,2,3-triazoles is the 1,3-dipolar Huisgen cycloaddition (reaction between azides and alkynes) [8]. Lately, this [3h-2] cycloaddition reaction has been aided by different [Cu(NHC)JX complexes [9]. The reactions between electron-rich, electron-poor and/or hindered alkynes 16 and azides 17 in the presence of low NHC-copper 18-20 loadings (in some cases even ppm amounts were used) afforded the 1,2,3-triazoles 21 regioselectively (Scheme 5.5 Table 5.2). 

COMPLEXES OF GOLD(I) WITH NITROGEN DONOR LIGANDS 55.9.1 Azide and Isocyanate Complexes... 

The normal azides of Au(I) and Au(III) have never been described, but a complex azidoaurate has been known since 1898, when Curtius and Rissom [62] reported on Doppelsalze von Platin- und Goldaziden (double salts of platinum and gold azides). The complexes were made in aqueous media from potassium azide and, e.g., H2PtCl6, according to... 

Curtius and Rissom discussed the nature of the above platinum complex in detail and drew an analogy to gold which reads Here again, by metathetic reaction of the slightly explosive potassium azide with gold chloride, is formed a highly explosive azide of gold besides potassium chloride. ... 

The tetraphenylarsonium salt of tetraazidoaurate(III) is made from 2.5 mmole potassium chloroaurate, KAuCU, which is dissolved in a small quantity of water. One hundred mmole of sodium azide is added to obtain a red solution. After filtering, tetraphenylarsonium chloride is added to precipitate the orange complex. It is recrystallized from acetone-water, or methylene chloride-hexane mixtures [139]. The colorless tetraphenylarsonium salt of diazidoaurate(I), [Ph4As] [Au (N3)2], is obtained by reacting a suspension of freshly prepared gold monochloride, AuCl (0.2 g = 0.9 mmole), and sodium azide (1.5 g = 23 mmole) in water-wet methylene chloride. Upon addition of... 

Mixed SAMs on gold electrodes from azido alkane thiols and various a>-functionalized alkanethiols were prepared. In the presence of copper(l) catalysts, these azide-modified surfaces are shown to react rapidly and quantitatively with terminal acetylenes forming 1,2,3-triazoles via click chemistry (Figure 6). In this way, thiol SAMs have been modified with complex functional molecules such as single-stranded DNA, porphyrin redox catalysts, and receptors for gold nanoparticles and other materials. 

Copper complexes containing abnormal imidazolylidene 4 were successfully applied to the [3+2] dipolar cycloaddition of azides and alkynes. " Related abnormal imidazolylidene gold(i) complexes showed good activity in the hydration of alkynes. However, the precursor complex required activation with a silver salt, which is likely to lead to carbene transfer (see Section... 

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