Theoretical investigation on the electronic structure of Pentacyanoferrate(II) Complexes with NO+, NO, and NO- Ligands. Redox interconversion, protonation and cyanide-releasing reactions

M.C. GONZÁLEZ LEBRERO, D. A. SCHERLIS, G. L. ESTIÚ, J. A. OLABE, D. A. ESTRIN

INORGANIC CHEMISTRY

Año: 2001 vol. 40 p. 4127 - 4133

0020-1669

Reaction pathways for the one- and two-electron reductions of [Fe(CN)5NO]2- have been investigated by meansof a density functional theory (DFT) approach combined with the polarized continuum model (PCM) of solvation.In addition, UV-vis spectroscopic data were obtained using ZINDO/S calculations including a point-charge modelsimulation of solvent effects. DFT methodologies have been used to assess the thermodynamical feasibility ofprotonation and cyanide-release processes for the reduced species. We conclude that [Fe(CN)5NO]3- is a stablespecies in aqueous solution but may release cyanide yielding [Fe(CN)4NO]2-, consistent with experimental results.On the other hand, the [Fe(CN)5NO]4- complex turns out to be unstable in solution, yielding the product ofcyanide release, [Fe(CN)4NO]3-, and/or the protonated HNO complex. All the structural and spectroscopic (IR,UV-vis) predictions for the [Fe(CN)5HNO]3- ion are consistent with the scarce but significant experimentalevidence of its presence as an intermediate in nitrogen redox interconversion chemistry. Our computed data supportan FeII(LS) + NO+ assignment for [Fe(CN)5NO]2-, an FeII(LS) + NO assignment for the one-electron reductionproduct, but an FeI(LS) + NO+ for the one-electron product after dissociation of an axial cianide, and an FeII +singlet NO- for the two-electron reduction species.