Reactivity of Hydrated Monovalent First Row Transition Metal Ions [M(H₂O)_n]⁺, M = Cr, Mn, Fe, Co, Ni, Cu, and Zn, n < 50, Toward Acetonitrile

Abstract

Reactions of [M(H2O)n](+), M = Cr, Mn, Fe, Co, Ni, Cu, and Zn, n < 50, with CH3CN are studied in the gas phase by Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry. Sequential uptake of 4-6 acetonitrile molecules is observed for all metals. Rate constants show a weak dependence on both the metal and the number of acetonitrile molecules already in the cluster. Nanocalorimetry yields the enthalpy of the first reaction step. For most metals, this is consistent with a ligand exchange of water against acetonitrile. For M = Cr, however, the strong exothermicity of ΔE(nc) = -195 ± 26 kJ mol(-1) suggests an electron transfer from Cr(+) to CH3CN. Exclusively for M = Zn, a relatively slow oxidation of the metal center to Zn(2+), with formation of ZnOH(+) and release of CH3CNH(•) or CH3CHN(•) is observed. Density functional theory molecular dynamics simulations and geometry optimizations show that charge transfer from Zn(+) to CH3CN as well as the subsequent proton transfer are associated with a barrier.

Microsolvation of Zn cations: infrared multiple photon dissociation spectroscopy of Zn+(H2O)n (n = 2–35)

“…46 Oxidation of Zn + (H 2 O) n to ZnOH + (H 2 O) m is also observed in the reactions with acetonitrile. 47 With 1-iodopropane, Zn + (H 2 O) n reacts efficiently to ZnI + (H 2 O) m , again with oxidation of the Zn centre. 48 These studies showed that hydrated monovalent zinc ions can be oxidized by suitable reactants, but the details of the reactions and their cluster size-dependence can be quite complex.…”

Photochemistry and spectroscopy of small hydrated magnesium clusters Mg+(H2O)n, n = 1–5

“…32 They also explained the switch off for the hydrogen loss process for larger clusters due to the barrier increase when the solvated electron moves beyond the third solvation shell. 15 Our group has a long history in studying the reactivity of hydrated metal ions, 13,16,[33][34][35][36][37][38][39][40][41][42][43][44][45][46][47] using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) which is well suited for this task as it allows highest mass resolution coupled with long storage times to allow multiple collisions with reactant gases. In the present study, we couple the mass spectrometer with a tunable optical parametric oscillator (OPO)/amplifier system to conduct photodissociation experiments.…”

Evidence for Electron Transfer in the Reactions of Hydrated Monovalent First-Row Transition-Metal Ions M(H2O)n+, M = V, Cr, Mn, Fe, Co, Ni, Cu, and Zn, n < 40, toward 1-Iodopropane

“…On the other hand, the second IE of zinc is even higher, and still Zn + (H 2 O) n are the most reactive species. The efficient ZnI + (H 2 O) m formation corresponds to the reactivity with acetonitrile, where Zn + (H 2 O) n is the only species for which hydroxide formation ZnOH + (H 2 O) m is observed …”

“…However, Zn­(I) cations are oxidized to Zn­(II), and a hydrogen atom is released upon uptake of a second HCl molecule . Monovalent hydrated zinc cations are also oxidized by acetonitrile in the gas phase . In studies of hydrated metal ions with small molecules like oxygen, nitrous oxide, carbon dioxide, and nitric oxide, different reactions depending on the metal and reactant were observed.…”