Complexes gold-cyano

Alkaline cyanide solutions are another common lixiviant for gold, giving complex cyano species in solution. These anionic complexes may be... 

Formigue and coworkers have successfully prepared asymmetrically substituted dithiolenes such as edt-CN (edt-CN = 2-cyano-l,2-ethylenedithiolate), tfadt and their square-planar nickel (49 and 50) and gold complexes . Both cis and trails isomers coexist and interconvert in solutions, while in the solid state the trails form is more commonly... 

NMR studies of13 C- or 15 N-enriched cyano gold complexes... 

Sodium cyanide is used in the extraction of gold and silver from ores because of the very stable linear cyano complexes formed with these metals. The molecular bonding for silver cyano complexes is drawn as [ N=C—Ag—C=N ] and similarly for gold complexes [ N C—Au—C N ]- (King, 1994). 

The compound 70 has also been reported showing the ambident character (both C- and N-coordination) of the cyano-stabilized ylide as ligand. The authors have also transposed their work concerning the keto-bis-ylide and palladium, with the synthesis of the C-bonded complex 71 or the new cycloplatinated or-thometallated compound 72. The latter by various treatments allows one to obtain other ylidic cationic complexes of platinum such as 73. A C,C,C-terdentate coordination of the keto bis-ylide, already observed with the palladium is also obtained from the reaction of 73 with gold derivatives. 

The majority of gold(I) carbene complexes are pure organometallic compounds and the are out of the scope of this work. Some halide or triphenylphosphine carbene complexes are known and they will be considered here. Nucleophilic addition of alcohols or amines to gold-coordinated isocyanides is one of the best-established methods to obtain gold carbene derivatives. The reaction of H[Au(CN)2] with propene oxide and estirene oxide yields (cyano)carbene complexes (380) avoiding the intermediate step.2257 A cyclic carbene compound is obtained by reaction of a dinuclear isocyanide with amine (Scheme 32).2258... 

This type of interaction is most commonly present in complexes containing tetracyanoaurate(III) anions, which can be present in the solid state in different association degrees. The simplest one is found in ]Cu(bipy)(H20)2 Au(CN)4 o.5][Au (CN)4]15 (bipy = 2,2 -bipyridine) [48] or in [ Cu(tmeda)( a-OH) 2Au(CN)4][Au(CN)4] (tmeda= N,N,N, N -tetramethylethylenediamine) [49], where part of the [Au(CN)4 anions form a linear trimeric anionic cluster via Au - N van der Waals interactions of the nitrogen atoms of two cyano groups trans to the gold(III) centers of two adjacent anions (Figure 5.24a). The interacting distances, 3.052(9) or 3.062 A, respectively, are... 

The low stability of two-coordinate complexes with respect to other possible structures is well illustrated by (he cyano complexes. Although sifver(f> and gold( ) form discrete bislcyano) complexes, solid KCufCNk possesses a chain structure in which the coordination number of the copperfl) is 3. 

A number of substitutions of alkylgold complexes by mercuric compounds have been examined by Gregory and Ingold44. The SE1 substitution of 1-cyano-l-carbethoxypentyl(triphenylphosphine) gold(I) has been described in Chapter 4, Section 2.3 (p. 32) and in the present section those substitutions proceeding by bimolecular mechanisms are discussed. 

We have recently been examining various inner-sphere adsorbed redox couples with the aim of deducing if such electron delocalization effects are indeed encountered. One type of candidate system is transition-metal cyano complexes. Some representative data for the Fe(CN)63>/1 "couple adsorbed at gold are presented in Figs. 2 and 3. 

The cyano- complex of univalent gold, Au(CN), has been mentioned in connection with recovery of the metal. Other stable derivatives of this valence state are complexes with gold-to-sulfur, gold-to-arsenic, and gold-to-phosphorus bonds. The structures pictured below may be regarded as representative ... 

The main use of NaCN is in the extraction of gold and silver from their ores by the formation of cyano complexes (Section 7-12). The ions Ag+, Hg2+, and Pb2+ give insoluble cyanides. 

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