Silver complexes, addition with

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. 

Organometallic complexes of copper, silver, and gold are ideal precursors for carbene complexes along with some C- and N-coordinated species. Their reactivity pattern, in particular in oxidative addition reactions, was the most comprehensively studied. 

Silver salts demonstrate how complexation enhances solubility. Figure 18-13 shows that silver will precipitate or dissolve in aqueous solution depending on the species that are present. Starting with a solution of silver nitrate, addition of aqueous NaCl causes AgCl to precipitate ... 

Based on the previously described silver complex [Au2Ag2(Q)f,s)4(MeCN)2 , the same reaction with CuCl in acetonitrile but with addition of an equivalent of pyrimidine leads to the polymeric [CuAu(C6F5)2(MeCN)((J.2-C4H4N2)]n [66]. The polymerization of this complex is produced by covalent copper-pyrimidine bonds. The environment of the copper centers also comprises unsupported gold-copper interactions of 2.8216(6) A and one molecule of acetonitrile, leading to a distorted tetrahedral arrangement (see Figure 6.26). 

The Complex Thiocyanates.—The alkali thiocyanates show a marked tendency to form double and complex salts with the thiocyanates of other metals. The double salts in general resemble in type the double halides. Such compounds as KAg(CNS)2 and K2Ag(CNS)3 may be considered as derivatives of di- and tri-thiocyanic acids, but in the salt (NH4)6Ag(CNS)6 the silver is not precipitated by the addition of chloride ion.8... 

Ag+ preferentially reacts with the analyte to form a soluble salt or complex. During this addition, Ag+ reacts with the analyte only, and not the indicator. But when all the analyte is completely consumed by Ag+ and no more of it is left in the solution, addition of an excess drop of silver nitrate titrant produces an instant change in color because of its reaction with the silver-sensitive indicator. Some of the indicators used in the argentometric titrations are potassium chromate or dichlorofluorescein in chloride analysis and p -dime thy la m i nobe nzalrho da n i nc in cyanide analysis. Silver nitrate reacts with potassium chromate to form red silver chromate at the end point. This is an example of precipitation indicator, where the first excess of silver ion combines with the indicator chromate ion to form a bright red solid. This is also known as Mohr method. 

An interesting variation on this theme has been reported by Lehn and coworkers. In 1986, they reported the synthesis of macrocycle 33, which consists of a zinc porphyrin bearing two linked cyclic binding subunits [87]. It was later found that addition of silver triflate to a solution of 33 in methanol resulted in the incorporation of a silver ion in each of the binding subunits [88], Thus, the complex may be represented as Ag+-P-Ag+. The porphyrin fluorescence of the silver complex was quenched, and transient absorption studies demonstrated that the porphyrin singlet state was quenched with a rate constant of 5.0 x 109 s 1 to yield a charge separated state Ag°-P+-Ag+. Some quenching of the porphyrin triplet... 

Pale and coworkers have demonstrated that silver acetylides may be synthesized with a variety of silver salts in the presence of base in a number of solvents. By treating 1 -hexyne in either deuterated benzene or DMF with silver triflate, the group was able to observe the formation of the Jt-alkyne-silver complex and subsequently the silver acetylide through the use of H, C, and Ag NMR. The incipient Jt-alkyne-silver complex is rapidly deprotonated on addition of diisopropylethylamine, to give the silver acetylide as a white precipitate (Scheme 1.33).89... 

In addition to the infinite tubes, polycatenanes, and polyrotaxanes, all of which are polymeric complexes, a great number of silver coordination polymers with ID, 2D and 3D framework structures have been reported more recently. Selected examples and their specific topologies of some of these are listed in Table 11.1. Schematic structures of the corresponding organic ligands are shown in Figure 11.23.9,58-75... 

A similar chiral silver(I) catalyst 21 was applied to the asymmetric addition of allyltributyltin to various aldehydes in an aqueous medium [28]. Shi et al. have shown that chiral silver complex 22, prepared from chiral bidentate phospho-ramide and AgOTf, is also an effective chiral catalyst for the allylation [29]. Chiral bis(oxazoline) ligands have found widespread use in asymmetric reactions catalyzed by chiral metal complexes, and C2-symmetric chiral bis(oxazoline)-Zn(OTf)2 complex 23 has been applied to catalytic enantioselective allylation of aldehydes with allyltributyltin (44) however, satisfactory enantioselectivity was not observed [30]. 

Obviously, addition of further AgBF to the mono-silver complex activates coordination to pyridine and formation of the dinuclear silverfl) complex. However, the dinuclear complex is in equilibrium with a trinuclear, triangular complex (see Figure 3.4). 

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