Silver complex formation

Silver complex formation with Cl and S(-II) is important. In oxic fresh waters [Ag ]/[Ag(I)dissoived] — 0.6. Table 10.11 lists recommended water quality criteria (concentrations that should not be exceeded to avoid ecologically harmful effects in fresh water) for Germany, the Netherlands, Canada, and Switzerland. 

Only three simple silver salts, ie, the fluoride, nitrate, and perchlorate, are soluble to the extent of at least one mole per Hter. Silver acetate, chlorate, nitrite, and sulfate are considered to be moderately soluble. AH other silver salts are, at most, spatingly soluble the sulfide is one of the most iasoluble salts known. SHver(I) also forms stable complexes with excess ammonia, cyanide, thiosulfate, and the haUdes. Complex formation often results ia the solubilization of otherwise iasoluble salts. Silver bromide and iodide are colored, although the respective ions are colorless. This is considered to be evidence of the partially covalent nature of these salts. 

To minimize the formation of fuhninating silver, these complexes should not be prepared from strongly basic suspensions of silver oxide. Highly explosive fuhninating silver, beheved to consist of either silver nitride or silver imide, may detonate spontaneously when silver oxide is heated with ammonia or when alkaline solutions of a silver—amine complex are stored. Addition of appropriate amounts of HCl to a solution of fuhninating silver renders it harmless. Stable silver complexes are also formed from many ahphatic and aromatic amines, eg, ethylamine, aniline, and pyridine. 

Halide Complexes. Silver hahdes form soluble complex ions, AgX and AgX , with excess chloride, bromide, and iodide. The relative stabihty of these complexes is 1 > Br > Cl. Complex formation affects solubihty greatiy. The solubihty of silver chloride in 1 A/ HCl is 100 times greater than in pure water. 

The thiosulfate ion, 820 is a stmctural analogue of the sulfate ion where one oxygen atom is replaced by one sulfur atom. The two sulfur atoms of thiosulfate thus are not equivalent. Indeed, the unique chemistry of the thiosulfate ion is dominated by the sulfide-like sulfur atom which is responsible for both the reducing properties and complexing abiUties. The abiUty of thiosulfates to dissolve silver haUdes through complex formation is the basis for their commercial appHcation in photography (qv). 

Complex formation reactions. These depend upon the combination of ions, other than hydrogen or hydroxide ions, to form a soluble, slightly dissociated ion or compound, as in the titration of a solution of a cyanide with silver nitrate... 

The following sections are concerned with the use of standard solutions of reagents such as silver nitrate, sodium chloride, potassium (or ammonium) thiocyanate, and potassium cyanide. Some of the determinations which will be considered strictly involve complex formation rather than precipitation reactions, but it is convenient to group them here as reactions involving the use of standard silver nitrate solutions. Before commencing the experimental work, the theoretical Sections 10.74 and 10.75 should be studied. 

In a complex-formation reaction the equivalent is most simply deduced by writing down the ionic equation of the reaction. For example, the equivalent of potassium cyanide in the titration with silver ions is 2 moles, since the reaction is ... 

Complex formation removes some of the Ag+ ions from solution. As a result, to preserve the value of Ksp, more silver chloride dissolves. Formation of a complex increases the solubility of a sparingly soluble compound. 

This group showed that isolable silver(I) diaminocarbene complexes can be use in situ instead of free carbenes, to generate the copper carbene complex. The silver salts that precipitates during the formation of the copper complex have not any negative effect on the conversion. This method is advantageous since most of the silver complexes are isolable, air-stable and easily obtained by treatment of the corresponding imidazohnium salt by 0.5 equiv of silver oxide (Scheme 53). The solid structure of 78 was analyzed by X-ray diffraction. 

The effect of complex formation on the solubility of a solid can be observed in the home. Silver dinnerware eventually becomes discolored by an unsightly black tarnish of Ag2 S, formed from the reaction of the silver surface with small amounts of H2 S present in the atmosphere. Silver sulfide is highly insoluble in water. Commercial silver polishes contain ligands that form strong soluble complexes with Ag ions. If a tarnished serving pan is rubbed with a polish, the black tarnish dissolves, returning the silver to its brilliant shine. 

A picture similar to that just described is seen for metal electrodes when the solution contains a complexing agent (e.g., for the silver electrode when KCN has been added to a AgNOj solution). Then the complex formation equilibrium... 

When ethylenediamine comes into contact with silver perchlorate it detonates. This accident is explained by the formation of an amine/silver complex that is unstable. 

Thermodynamics of complex formation of silver with several ligands such amines,368 hindered pyridine bases,369 nitrogen donor solvents,370 and azoles371 have been carried out. Other studies include the secondary-ion mass spectra of nonvolatile silver complexes,372 the relationship between Lewis acid-base behavior in the gas phase and the aqueous solution,373 or the rates of hydride abstraction from amines via reactions with ground-state Ag+.374... 

Other polydentate ligands are polyamines and related ligands. Stability constants of silver(I) complexes with polyamines in dimethyl sulfoxide,419 A-methyl-substituted 4-methyldiethylene-triamines,420 or ethylene- or N- or C-methylated ethylenediamine in aqueous solution have been reported.421 The structure of the silver 1,3-diaminopropane complex, [Ag NH2(CH2)3NH2 ]-C104,422 and complex formation with 1,4-diaminobutane and 1,5-diaminopentane have been reported.423 A dinuclear silver(I) compound with ethylenediamine [(enH)Ag(en)Ag(enH)2]4+ has... 

They have also examined the formation of the ir-complex between the silacalixarenes and silver cation by FAB mass spectrometry. Similar 77-complex formation with silver cation was observed for hexasila [2,2,2]paracyclophanes 37 (41). 

A silver-containing solution was basified with sodium hydroxide, and after filtration, ammonia solution was used to wash residual silver from the filter. Hydrazine sulfate was then added to precipitate metallic silver and when the mixture was heated it exploded. This may have been caused by formation of silver nitride and/or hydrazine-silver complexes, both of which are explosively unstable. 

An associative mechanism is supported, consistent with a low-spin d configuration. Other ligands such as arsenite reduce Ag(OH>4 in a rapid second-order reaction. It is uncertain whether it occurs via complex formation. Silver(III) macrocycles including porphyrin complexes have been characterized. 

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