Gold complexes nitriles

The soft Au+ forms relatively few complexes compared with those of phosphines. Complexes with ammines, nitriles and diazoles like Au(NH3)2 and Au(RCN)2 are known but little studied. In linear Au(NH3)2, Au-N is 2.01-2.03 A [70a], [Au(NCPh)2]+ has been used as a labile source of other gold complexes [70b]. AuCl(piperidine) is a monomer with weak tetra-meric association in contrast AuX(py) (X = Cl, Br, I) are [Aupy2]+[AuX2] with a chain structure in the solid state (and Au-Au interactions), suggesting a close balance between factors for molecular and ionic structures [70c] (note also the tetrahydrothiophene complexes in section 4.10.6). 

Apart from these findings, Echavarren and coworkers found a different strategy to isolate catalytically active gold(l) phosphine and NHC complexes [25]. They were able to isolate an array of different cationic gold complexes with noncoordinating anions, typically SbFs , which bear a nitrile ligand (see Scheme 9.9). 

Owing to the good ligand properties of isocyanides for complexation of gold(i), complexes of the type [(RNC)2Au]+X are readily available through a variety of synthetic routes. One new approach is the substitution of organic nitriles. The reaction is carried out in acetonitrile and gives quantitative yields (Equation (43)).2... 

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. "... 

A further example for a metal-initiated reaction sequence providing an indole-inspired NP-based complex scaffold was reported by Van der Eycken and coworkers [7]. In this case, a Ugi reaction provided the desired substrate for the sequence of cyclization reactions initiated by the activation of the acetylene with a gold catalyst. The Ugi four-component reaction employed the indole-carboxaldehyde 12, the nitrile 13, amine 14, and carboxyhc acid 15 and led to the formation of the intermediate 16. In the presence of a gold(I) catalyst, instead of the expected indoloazepinone that could be formed via an endo-dig cyclization, a tetracyclic spiroindoline 17 was formed diastereoselectively (Scheme 13.3). 

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