Coordination Chemistry of Silver Cations

While in pure solvents Ag+ is known to be tetrahedrally coordinated, in the presence of ligands
such as ammonia it forms linear complexes, usually explained by the ion's tendency toward sd-hybridization.
To explore this disparity, we have investigated the reaction of ammoniated silver cations Ag+(NH3)n, n =
11−23, with H2O as well as the complementary process, the reaction of Ag+(H2O)n, n = 25−45, with NH3
by means of FT-ICR mass spectrometry. In both cases, ligand exchange reactions take place, leading to
clusters with a limited number of NH3 ligands. The former reaction proceeds very rapidly until only three
NH3 ligands are left, followed by a much slower loss of an additional ligand to form Ag+(NH3)2(H2O)m clusters.
In the complementary process, the reaction of Ag+(H2O)n with NH3 five ammonia ligands are very rapidly
taken up by the clusters, with a much less efficient uptake of a sixth one. The accompanying DFT calculations
reveal a delicate balance between competing effects where not only the preference of Ag+ for
sd-hybridization, but also its ability to polarize the ligands and thus affect the strength of their hydrogen
bonding, as well as the ability of the solvent to form extended hydrogen-bonded networks are important.