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(+)(NH(3))(n)(), n = 11-23, with H(2)O as well as the complementary process, the reaction of Ag(+)(H(2)O)(n)(), n = 25-45, with NH(3) by means of FT-ICR mass spectrometry. In both cases, ligand exchange reactions take place, leading to clusters with a limited number of NH(3) ligands. The former reaction proceeds very rapidly until only three NH(3) ligands are left, followed by a much slower loss of an additional ligand to form Ag(+)(NH(3))(2)(H(2)O)(m)() clusters. In the complementary process, the reaction of Ag(+)(H(2)O)(n)() with NH(3) 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.

Aqueous chemistry of transition metals in oxidation state (I) in Nanodroplets.

"Nanodroplets" consisting of a central ion surrounded by a solvation shell of water molecules provide an interesting medium for studies of aqueous transition-metal chemistry in the unusual oxidation state (I). While VI undergoes efficient, solvent shell dependent redox reactions to VII and VIII, the absence of any similar reactivity in aqueous CrI, Mn1, FeI, CoI, NiI, and CuI clusters is explained by a rapid precipitation of the corresponding single monochloride molecules from the nanosolutions.

Single-molecule precipitation of transition metal(I) chlorides in water clusters.

Metal ions in unusual oxidation states can be introduced into water clusters using a standard laser vaporization source. Such nanosolutions of a single ion in typically 50 water molecules are comparable to a 1 M bulk solution, and their chemistry can be studied in the ion trap of a Fourier transform ion cyclotron resonance mass spectrometer. We find that a strong acid like hydrogen chloride oxidizes the early transition metal vanadium to the more common +III state, while later first row transition metals retain their unusual +I oxidation state, and the binary metal chlorides M(I)Cl precipitate.