Argentation—the Formation of Silver Complexes

Several analytical and separation techniques are based on the reversible formation of complexes between alkenes and Ag+ ions. Analytical methods for terpenes, unsaturated acids and esters, and other unsaturated nonpolar compounds are based on the use of Ag -impregnated materials for thin-layer (TLC) and high-pressure (HPLC) as well as gas-liquid (GLC) chromatography. GLC measurements done some years ago suggest that the affinity decreases with additional substituents, but increases with strain.  

An NMR study in methanol showed a similar trend in relative stability of the Ag(I) 

The structure and stability of alkene-Ag complexes has also been examined by computation. MP2/SBK( f) calculations indicate that three ethene molecules are accommodated at Ag+ with Af of —30 3kcal/mol, but subsequent ethenes are less strongly bound. The computations find stronger complexation with alkyl-substituted alkenes in the gas phase, which is in contrast to the trend in the solution stabilities. This might be the result of the greater importance of solvation in the liquid phase, whereas polarization might be the dominant factor in the gas phase. 

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