Electronic d-d spectra and ligand-dissociation rates of pentacyanoruthenate(II) ions

Abstract

The electronic spectra of a series of [Ru(CN)₅L]^n– complexes (L = H₂O, NH₃, pyrazine, dimethyl sulphoxide, or CN^–) have been measured in aqueous solution. The d-d bands were assigned on the basis of a ligand-field model for tetragonally distorted octahedra and the energy of the transitions, which depends on the nature of L, were found to correlate with the rate constant for the dissociation of L from [Ru (CN)₅L]^n–, k_–L. Comparisons are made with the similar [Fe(CN)₅L]^n– series. A new value of 10Dq, 4.2 µm^–1, is proposed for [Ru(CN)₆]^4–, which is significantly higher than that corresponding to [Fe(CN)₆]^4–, as expected from ligand-field theory.