Silver ll Complexes

Several silver(I) complexes of the macrocyclic Schiff base derived from the [2+2] condensation of terephthalaldehyde and 3-azapentane-1,5-diamine or A,A -bis(3-aminopropyl)methylamine have been described.509,510 The reaction of 2,ll-diaza-difluoro-m-[3,3]-cyclophane with 2,6-bis (bromomethyl)pyridine lead to the 3 + 3 addition product, which gives a complex with two silver... 

Many of the synthetic routes parallel those used to prepare alkene complexes c platinum(II). Replacement of chloride ion in PtClJ- by a water soluble alkyne is a frequentl used method (equation 266), 809 812 or the reaction can be assisted by the use of a silver salt t facilitate halide displacement (equation 267).813 With hexafluorobutyne-2 the five-coordinat adduct can be isolated before it converts into the vinyl complex (89 equation 268).814 Alkyne displace alkenes from platinum(ll) complexes. 

Most of the diphosphine complexes of silver known are of the type AgXP2, where X is a halide and P2 is a diphosphine. In general, they adopt dimeric structures in the solid state, with the exception of the silver chloride complex of 2,ll-bis(diphenylphosphinomethyl)benzo[c]-phenanthrene which is monomeric. 

The obtained amino functionalised imidazolium salts could be used to generate the corresponding palladium(ll) carbene complexes using the silver(l) complexes as carbene transfer agents. Application of these palladium(ll) complexes (predominantly in situ) in asymmetric allylic alkylation reactions between ( )-l,3-diphenylprop-3-enyl acetate and dimethyl malonate (a standard reaction for this catalytic process [145]) gave up to 80% ee,... 

Formation of the palladium(n) complex does not require the silver(I) complex, but can be achieved by reaction of the pincer imidazolium salt with [PdjCdbalj] [136]. As already described for the corresponding CT4,C pincer complex, the C,C,C palladium(ll) complex displays a conformational flexibility with 8// of 51.6 kJ/mol for the C,N,C pincer complex and 74.5 kJ/mol for the C,C,C pincer complex. This difference in enthalpies is unexpected and was explained later by the same authors [503] as stemming from a counter anionic... 

According to this postulate, the difference between coupling with silver and disproportionation with iron rests on the decomposition of the alkylmetal intermediate in Equation 50. Indeed, it has been shown separately in Equation 42 that the decomposition of alkylsilver(I) proceeds by reductive coupling. Unfortunately, the highly unstable alkyliron intermediate in Scheme 6 is not yet accessible to independent study, but the somewhat analogous dialkylmanganese(ll) species in Equation 51 undergoes similar reductive disproportionation by a mechanism S) reminiscent of dialkylplatinum(ll) complexes described in Equation 7. 

The test identifies the substance to be examined as a salt of silver (Ag+). At the present silver is referenced in only one monograph, silver nitrate. This salt is sold in sticks, called Lapis or Lapis lunaris, and is used for the treatment of warts. Silver can exist both as silver(l) and silver(ll), but since the latter is less stable, silver(I) dominates. It is a noble metal meaning that it is most stable in oxidation state 0, its metallic form. So, contrary to most metals, it does not have at tendency to be oxidized to its ionic form and thereby corrode. Silver nitrate and fluoride are soluble, while silver nitrate, acetate, and sulfate have limited solubility. All other salts are insoluble but are, however, capable of forming many soluble complexes. The insolubility of the chloride salt and its ability to form a soluble nitrate complex are useful in identification. 

The use of phenyl triflate (2) was favoured over phenyl iodide, which gave very poor enantioselection, and it was postulated that employing the triflate allows the reaction to proceed by the cationic as opposed to the neutral pathway (Scheme 11.5). The cationic pathway was proposed as early as 1990 and begins with the dissociation of X (X = triflate or a halide in the presence of a halide scavenger such as silver or thallium cations) from the cationic complex with the accompanying counterion X (X = halide or triflate) [9]. Complexation of the alkene... 

Redox-Structural Correlations in Metal Thioether Mactocyclic Complexes The Stabilisation of Mononuclear Silver(ll) and Gold(ll)... 

Further silver(II) bis(dithiocarbamate) complexes [Ag(S2CNR2)2] (R = Pr, i-Pr, Cy) and their Py adducts have purportedly been prepared in 7V-(4-methoxyben-zlidene)-4 -butylaniline (MBBA) orientated in nematic glasses and organic solvents the equilibrium between them and silver(l) species being studied (1808). Also, as detailed above, [Ag6(S2CNEt2)6(SCN)4] has been proposed to contain both silver(I) and silver(ll) centers, the presence of the latter being based on ESR data (1797). 

The persulphate oxidation of Ag(I) is indicated by the black colour seen when silver ions catalyse the persulphate oxidation of Cr(III) or Mn(II). The presence of a chelating ligand is expected to stabilise silver(ll). Dipyridyl forms complexes with silver nitrate readily. Persulphate oxidises Ag(I) in the complex to Ag(II) replacing the nitrate as a counter ion. 

Anderson WA, Catty AJ et al (1969) Coordination complexes of acetylene diphosphines. Part 111. Silver(l) and mercuty(ll) complexes. Can J Chem 47 3361-3366 James SL, Xu X et al (2003) Phosphine-based coordination cages and nanoporous coordination polymers. Macromol Symp 196 187-199... 

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