Resonance-Raman and infrared studies of cyanide-bridged dimetal complexes

Abstract

Raman and i.r. spectra have been determined in the ν(CN) region of the CN-bridged dimetal complex anions [(NC)5FeII(CN)CoIII(CN)5]6– and [(NC)5FeIII(CN)CoIII(CN)5]5–. The spectra show bands at 2 130 and 2 185 cm–1, respectively, which are assigned to the stretching modes of the bridging CN groups. Similar modes are assigned at 2 134 and 2 182 cm–1 in the spectra of the two short-lived reaction intermediates [(NC)5FeII(CN)CoIII(edta)]5– and [(NC)5FeIII(CN)CoIII(edta)]4–, respectively (edta =NNN′N′-ethylenediaminetetra-acetate). The terminal CN stretching modes all occur at much lower wavenumbers. ν(CN) Raman bands of the bridging group in both [(NC)5FeII(CN)CoIII(CN)5]6– and [(NC)5FeII(CN)CoIII(edta)]5– show resonance enhancement associated with the absorption bands at 395 and 565 nm, respectively, indicating that these bands may be assigned to a charge-transfer transition of the type FeII→CoIII through the CN bridge.