title: Accurate measurement of the relative bond energies of CO and H2O ligands in Fe+ mono- and bis-ligated complexes.
abstract: The systems Fe(H(2)O)(n) (+)/CO[bond]H(2)O and Fe(CO)(n) (+)/CO[bond]H(2)O (n = 1 and 2) were investigated in a triple cell Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer. Using mixtures of CO with a very small amount of water, the ligand exchange equilibrium was reached, allowing experimental determination of the relevant equilibrium constants and free energies of reaction. Quantum chemical calculations at the B3LYP level of theory on the reactant and product species allowed us to determine the entropic terms and to derive the relative bond energies of CO and H(2)O in the mono- and bis-ligated complexes. For n = 1, H(2)O is more strongly bound to Fe(+) than CO by 4.1 +/- 1.6 kJ x mol(-1) at 298 K. For n = 2, at the same temperature, H(2)O is more strongly bound than CO to (H(2)O)Fe(+) by 7.6 +/- 1.6 kJ x mol(-1), and to (CO)Fe(+) by more than 20.1 kJ x mol(-1).
authors.affiliation: Laboratoire de Chimie Physique, UMR 8000, CNRS, Bât. 350, Université Paris-Sud, 91405 Orsay cedex, France. sophie.lecaer@lcp.u-psud.fr
authors.forename: Sophie
authors.initials: S
authors.lastname: le Caër
authors.forename: Michel
authors.initials: M
authors.lastname: Heninger
authors.forename: Philippe
authors.initials: P
authors.lastname: Maître
authors.forename: Hélène
authors.initials: H
authors.lastname: Mestdagh