Disilver complex

Novel triply-bridged disilver complexes [Ag2(p2-dppa-/>,/> )3(anion)2] (14) form... 

The larger-ringed macrocycles of (53a-d) form binuclear complexes with alkali metal, alkaline earth, silver(I) and lead(II) cations.68,192 The two 18-membered rings are large enough to allow for cations as large as Rb+ to be incorporated within their cavity, with a net result of increasing the metal-metal separation. Thus, crystal structure data for the disodium complex of (53a) indicate the sodium ions to be 6.40 A apart,193,194 compared to a 3.88 A separation found for the aforementioned disilver complex of (52a). Heteronuclear complex formation has also been observed, e.g. with both Ag+ and Pb2+ incorporated in the same cryptand.192... 

Figure 6-33. When a larger metal ion such as silver(i) is used as a template, the condensation of 2,6-diacetylpyridine with the diamine gives a complex of the larger [2+2] macrocycle 6.34. Actually, the macrocycle 6.34 is isolated as a disilver complex.

Ag(I) ions have been used to direct [2-1-2] photodimerizations in solids. Argentophilic forces (i.e., Ag- Ag interactions) were exploited by MacGilhvray and coworkers to assemble and stack a stilbazole (4-stilbz) for reaction Reaction of Ag(I) trifluoroacetate with 4-stilbz produced a disilver complex that organized two pairs of 4-stilbz. The Ag- Ag interaction displayed a metal-metal separation of 3.41 A while the C=C bonds were crisscrossed and separated by 3.82 A (Scheme 6a). The corresponding head-to-head cyclobutane was generated quantitatively in a SCSC reaction. The formation of the photoproduct was ascribed to pedal-like rotation of the C=C bonds in the solid. A similar complex was subsequently used to achieve the first photodimerization of terminal olefins in a solid. Reaction of Ag(l) chlorate with 4-vinylpyridine (4-vp) afforded a disilver complex (Scheme 6b) that generated c/x-l,2-bis(4-pyridyl)cyclobutane stereospecifically and in quantitative yield. 

The 1,2,4-triazolium salt 102 (Figure 1.10) was prepared by Bertrand and co-workers. Even if all attempts to isolate the free dicarbene by deprotonation of the dication failed thus far, it was possible to obtain the mono- and disilver complexes by deprotonation and metalation of the carbon atoms of the hete-rocycle. Peris and co-workers obtained the diiridium complex by reaction of 102 (R = Me) with two equivalents of IrCl(COD)]2 in the presence of KOt-Bu. A heterobimetallic Ir Rh complex was obtained by successive reaction of 102 with [IrCl(COD)]2 and [RhCl(COD)]2. ... 

Selenium occurs in the slimes as intermetallic compounds such as copper silver selenide [12040-91 -4], CuAgSe disilver selenide [1302-09-6], Ag2Se and Cu2 Se [20405-64-5], where x < 1. The primary purpose of slimes treatment is the recovery of the precious metals gold, silver, platinum, palladium, and rhodium. The recovery of selenium is a secondary concern. Because of the complexity and variabiUty of slimes composition throughout the world, a number of processes have been developed to recover both the precious metals and selenium. More recently, the emphasis has switched to the development of processes which result in early recovery of the higher value precious metals. Selenium and tellurium are released in the later stages. Processes in use at the primary copper refineries are described in detail elsewhere (25—44). 

The reaction of the cyclic P3-ligand l,3,5-triphospha-2,4,6-trisilacyclohexane with AgOTf results in the synthesis of complex (101) with a cyclic P6 ligand.794 Optically pure (S,5)-(+)-(PPh2CH2CH2)2(PPhCH2CH2PPh) spontaneously self-assembles into left-handed double-stranded D2-double helix (102) and C2-side-by-side helix conformers of the disilver(I) cation.795... 

Trinuclear disilver(I)-copper(II) complexes, [Ag(PPh3)2]2[Cu(mtm)2] and [Ag2(dppm)2] [Cu(mtm)2] (mtm = [bis(methylthio)methylene]malonate), have been prepared (Scheme 5). 

Both the disilver derivative and its precursory dipyridine complex are highly explosive and extremely shock-sensitive when dry. 

This and its pyridine complex explode violently if heated or struck [1] (but see below). More data on the stability of disilver ketenide and its complexes is contained in [2],... 

Dehalogenation has also been employed in the preparation of cyclobutenes. For example, stereoisomerically pure l,2-dichloro-3,4-dibromocyclobutane (18) reacts with 0.5% lithium amalgam in diethyl ether to give the nnf/ -tricyclooctadiene 32, which is isolated as its corresponding disilver(I) complex 31.11 However, similar treatment only converts tetrachlorocy-clobutane (16) to yyn-tricyclooctadiene 34 in very low yield.11... 

A solution of m-l,2-dichloro-cw-3,nwv-4-dibromocyclobutane (18 1.4 g, 5 mmol) in anhyd Et2O(30 mL) was shaken with lithium amalgam (0.5% lithium. 35 g) in a glass stoppered flask until the exothermal reaction ceased and then mechanically stirred for 12 h. The mixture was steam-distilled and the ethereal layer was shaken with aq AgN03 to give the disilver(I) complex 31 of the product yield 0.55 g (50%) mp 150 C, The disilver(I) complex was treated with brine to give the product 32. 

Disilver Aeetylide + Silver Nitrate (Complex) (Silver Acetylide-Silver Nitrate), AgaCa AgNOj or AgjCjNOj, mw 409.67, N3.42%. Wh pdr,d 5.38(Ref 5) mp-deton ca 212 Ref 6). 

Disilver Acetylide 4 Six Silver Nitrates (Complex), AgjCj+6AgNOs or Cj Ag N60lft, crysts, mp-when heated to 308-327°it melts and then suddenly decomp with evoln of red fumes. Can be prepd by passing CaHa through a 30 soln of AgNOj in HaO or N/l HNOr It is not expl... 

Disilver Acetylide 4 Silver Iodide (Complex), AgjCa. Agl or [ AgjCj] I gm vety expl ppt. Can be prepd from CaHa and an ammoniacal soln of freshly prepd Agl, taken in excess Refs l)Beil 1,241 2)M.Berthelot M-... 

Dlsilver Acetylide 4 Disilver Sulfate Complex, (AgaCa). Aga904 or (Ag3Ca)Ag904, wh ppt, deton weakly in vacuo. Can be prepd by treating CaHa with an excess of silver sulfate in soln... 

Disilver Oxide + Acetylene + Di silver Chrom-ote (Complex), AgaO + C2H2 + Ag2Cr04. Or-red crysts, expl ca 157°. Can be prepd from acetylene and a boiling soln of silver bichromate... 

Two Disilver Acetylides + Silver Chloride (Complex), (Ag2C2)2. AgCl or Ag2C2 +... 

Silver porphyrins are interesting because of the existence of disilver(I), paramagnetic silver(II), and diamagnetic silver(III) complexes which has been known for a long time [7, 8]. The latter are favorably prepared by electrochemical [299] or peroxodisulfate [300-302] oxidation of silver(II) porphyrins. The Ag(III) porphyrins were used for and 2H resonance experiments [299] on one hand and for the determination of monomer-dimer equilibria [301] or self-exchange rate constants [301] at water-soluble silver porphyrins. 

Blues, E. T. et al., J. Chem. Soc., Chem. Comm., 1974, 466—467 Both the disilver derivative and its precursory dipyridine complex are highly explosive and extremely shock-sensitive when dry. 

Different metal complexes have shown the ability to catalyze these imination reactions, such as rhodium, copper, and iron.22 In 2005, Bolm found that the disilver(I) complex described in Section 6.2.2 catalyzes the imination of sulfides and sulfoxides... 

Similar to that of the Bu jtpy-silver catalyst, the crystal structure of the bath-ophenanthroline-silver complex has a disilver(I) core and two BP ligands stacked over each other, similar to the corresponding palladium(II)-BP complex. 

The silver-silver distance is 3.386 A, indicating a weak silver-silver interaction (Fig. 6.3). Observing the disilver structure for the second time, the authors studied the importance of the disilver structure on reactivity. By testing different phenanthrolines, they found that 2,9-substituted phenanthrolines did not catalyze the amination reaction. This result was supported by structural evidence—the silver-2,9-dimethyl-phenanthroline complex did not form disilver structure two ligands coordinated one silver in a tetrahedral geometry, blocking the approach of any other molecule to the silver center. Even one bulky mesityl group in the 2 position inhibits the reactivity completely (Scheme 6.6). 

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