Observations on Silver Salt Metathesis Reactions with Very Weakly Coordinating Anions

Article abstract of DOI:10.1021/ja00199a025

Silver salt metathesis reactions using the very weakly nucleophilic anion B11CH12(1-) reveal several unexpected features of this otherwise familiar reaction.In contrast to AgClO4, which undergoes rapid metathesis with IrCl(CO)(PPh3)2, the silver carborane salt Ag(B11CH12) forms a very stable 1 : 1 adduct having iridium to silver metal-metal bonding.With Fe(Cp)(CO)2I, a long-lived, isolable intermediate is formed during the first minutes of reaction.The stoichiometry is also 1 : 1 but the structutre is almost certainly that of a halide-bridged adduct:Fe(Cp)(CO)2I*Ag(B11CH12).Eventual metathesis occurs depositing AgI and giving Fe(Cp)(CO)2(B11CH12), which has been the subject of an X-ray crystal structure determination.This work shows that the role of the counterion to silver is much more important to the mechanism and outcome of silver halide abstraction reactions than has previously been recognized and sets the stage for detailed mechanistic studies.