Silver complexes aromatic

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. 

T-7T Stacking or jt-jt interactions are important noncovalent intermolecular interactions, which contribute much to self-assembly when extended structures are formed from building blocks with aromatic moieties. In relation to the rich variety of jt-jt stacking in the crystal structure of silver complexes of phenylenediethynide, related silver complexes of phenylethynide and its homologues with different substituents (-CH3, -QC or the -CH3 group in different positions (0m-, p-) are investigated. 

Activation of the acetylene by coordination of the triple bond to the silver cation enables a 5-endo-dig cydization via nucleophilic attack of the amine [14]. Protonation of the resulting vinyl silver complex leads to an iminium ion. Subsequent p-hydride elimination affords metallic silver and a pyrrylium ion which aromatizes by proton loss to the pyrrole. For trimethylsilyl-substituted homopropargylamines (R = SiMes), the resulting pyrrole (R = SiMe3) undergoes protodesilylation to the 1,2-disubstituted pyrrole. 

The K value for the silver complex of an acetylene, hex-3-yne, as determined by the distribution method 14>, was found to be 19.1, i.e. smaller than those of alkenes such as the pentenes and cyclohexene, but greater than those of aromatic hydrocarbons 1S). A later study of silver-acetylene complexes 16> using the more rapid solubility technique of Andrews and Keefer 1S> gave rise to quasi thermodynamic equilibrium constants , Ka (as opposed to K) for various methyl substituted hex-3-ynes and hept-2-yne. There was good agreement for the K values for hex-3-yne for the two different methods in each case, replacement of an a-hydrogen atom by a methyl group caused a decrease in the value of Ka, similar to that observed in alkenes. Values of AH approximated to 19-21 kJ mole-1. 

Despite the fact that silver(I)-aromatic complexes of benzene, cyclo-phane, indene, acenaphthene, naphthalene, and anthracene have been reported, the corresponding organometallic polymers of pyrene (Lag) and peiylene (L ) have been crystallographically characterized only recently (187). X-ray structure determination of the complex with pyrene [Ag2(Le8)(C104)2] reveals that it exists in the solid state as an... 

As well as the cr-complexes discussed above, aromatic molecules combine with such compounds as quinones, polynitro-aromatics and tetra-cyanoethylene to give more loosely bound structures called charge-transfer complexes. Closely related to these, but usually known as Tt-complexes, are the associations formed by aromatic compounds and halogens, hydrogen halides, silver ions and other electrophiles. 

In TT-complexes formed from aromatic compounds and halogens, the halogen is not bound to any single carbon atom but to the 7r-electron structure of the aromatic, though the precise geometry of the complexes is uncertain. The complexes with silver ions also do not have the silver associated with a particular carbon atom of the aromatic ring, as is shown by the structure of the complex from benzene and silver perchlorate. ... 

Olefin Complexes. Silver ion forms complexes with olefins and many aromatic compounds. As a general rule, the stabihty of olefin complexes decreases as alkyl groups are substituted for the hydrogen bonded to the ethylene carbon atoms (19). 

Among the compounds that form complexes with silver and other metals are benzene (represented as in 9) and cyclooctatetraene. When the metal involved has a coordination number >1, more than one donor molecule participates. In many cases, this extra electron density comes from CO groups, which in these eomplexes are called carbonyl groups. Thus, benzene-chromium tricarbonyl (10) is a stable compound. Three arrows are shown, since all three aromatic bonding orbitals contribute some electron density to the metal. Metallocenes (p. 53) may be considered a special case of this type of complex, although the bonding in metallocenes is much stronger. 

Free-radical acyloxylation of aromatic substrates has been accomplished with a number of reagents including copper(II) acetate,benzoyl peroxide-iodine, silver(II) complexes, and cobalt(III) trifluoroacetate. ... 

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