Gold complexes imidazoles

A Au mdssbauer study of reaction products of trimeric l-benzyl-2-gold(I)-imidazole leading to Au carbene or Au imidazoline complexes and trinuclear Au " imidazolyl derivatives. X-Ray crystal structure of [ (p-l-benzylimidazolato-N, C )Au 3l2j. Journal of Organometallic Chemistry, 470, 275-283. 

Gold complexes like [l-(2-hydroxy-cyclohexyl)-3-(acetophenone)imidazol-... 

Carbene complexes have also been prepared by transmetallation reactions. Lithiated azoles react with gold chloride compounds and after protonation or alkylation the corresponding dihydro-azol-ylidene compounds, e.g., (381) or (382), are obtained.22 9-2264 Silver salts of benz-imidazol have also been used to obtain carbene derivatives.2265 Mononuclear gold(I) carbene complexes also form when trimeric gold(I) imidazolyl reacts with ethyl chlorocarbonate or ethyl idodate.2266,2267 The treatment of gold halide complexes with 2-lithiated pyridine followed by protonation or alkylation also yields carbene complexes such as (383).2268 Some of these carbene complexes show luminescent properties.2269-2271... 

A whole series of (imidazol-2-ylidene)gold(i) complexes with the 1 1 stoichiometry has been prepared from the readily available silver chloride adducts, which upon reaction with (Me2S)AuCl, followed by chloride metathesis, give the complexes shown in Scheme 60. 

Bis[Ar,Ar -di(2-pyridyl)- and -di(2-pyridyl-methyl)-imidazol-2-ylidene]aurate(i) tetrafluoroborates have been prepared from the analogous silver complexes on reaction with (tht)AuCl and their structures determined. The configuration of the cations with sterically well-protected two-coordinate gold centers shows no anomalies. However, fascinating structures are found for the adducts with silver tetrafluoroborate obtained as acetonitrile... 

Selected mono- and di(A,A-diorganyl-imidazol-2-ylidene)gold(i) complexes have been investigated for their antibacterial activity. Positive effects against Staphylococcus and Enterococcus bacteria, Escheria coli, and Pseudomona aeruginosa were encountered in particular with the A-substituents being mesityl or benzyl (Equation (51)).278... 

Imidazolium ligands, in Rh complexes, 7, 126 Imidazolium salts iridium binding, 7, 349 in silver(I) carbene synthesis, 2, 206 Imidazol-2-ylidene carbenes, with tungsten carbonyls, 5, 678 (Imidazol-2-ylidene)gold(I) complexes, preparation, 2, 289 Imidazopyridine, in trinuclear Ru and Os clusters, 6, 727 Imidazo[l,2-a]-pyridines, iodo-substituted, in Grignard reagent preparation, 9, 37—38 Imido alkyl complexes, with tantalum, 5, 118—120 Imido-amido half-sandwich compounds, with tantalum, 5,183 /13-Imido clusters, with trinuclear Ru clusters, 6, 733 Imido complexes with bis-Gp Ti, 4, 579 with monoalkyl Ti(IV), 4, 336 with mono-Gp Ti(IV), 4, 419 with Ru half-sandwiches, 6, 519—520 with tantalum, 5, 110 with titanium(IV) dialkyls, 4, 352 with titanocenes, 4, 566 with tungsten... 

Mono(A, A -diorganyl-imidazol-2-ylidene)gold(I) complex, reactivity, 2, 293... 

Similar carbene complexes of silver(l) and gold(l) are observed when catechole is used as the scaffold. Synthesis of the bis-imidazohum salt follows the established protocol with bis-iodoethyl catechole and A-(l-naphthylmethyl)-imidazole as the starting materials [214], Reaction with silver(l) oxide and subsequent carbene transfer to copper(l) iodide yields the corresponding silver(l) and copper(l) carbene complexes. 

Even a rod-like backbone derived from acetylene is conceivable and has been realised by Liu et al. [367] starting from l,4-dichlorobutin-2. The usual reaction with methyl imidazole and subsequent reaction with silver(l) oxide and carbene transfer to gold(I) [Au(SEtj)Cl] makes the dimeric silver(I) and gold(l) complexes accessible featuring argentophilic and aurophilic interactions, respectively. 

The two carbene units can be embedded in a (macro)cyclic ring system known as a cyclophane. A standard procedure for the synthesis of such a system starts with a,a -dibromoxylene and potassium imidazolide [368]. Cychsation can be achieved by reacting the bis-imidazole compound with a second equivalent of a,a -dibromoxylene (see Figure 3.116). The cyclic bis-imidazolium cyclophane can then be reacted with paUadium(II) acetate to form the palladium complex [369,370]. The silver(I) and gold(I) complexes are accessible from the reaction with silver(I) oxide [371] and the usual carbene transfer reaction to gold(I) [372]. 

The bis-carbene complexes 55-57 readily undergo oxidation to gold(III) complexes (68, 69, Scheme 1). In 68 and presumably in 69, the gold(III) has a trans configuration, but the stereochemistry cannot be deduced from the spectrum. The trimeric imidazole complex 58 gives an incompletely oxidized form, readily recognized from its composite Mossbauer... 

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