Vibrational Spectrum and Structure of K3Ir(CN)6, K3Rh(CN)6, and K3Co(CN)6

The infrared spectra of crystalline K3Ir(CN)6 and K3Rh(CN)6 have been recorded. This information is combined with Raman data of other workers to yield a nearly complete assignment of the fundamental vibrational frequencies of the M(CN)63— ions. Force constants have been calculated for these ions and that of Co(CN)63— from previously reported spectra, and it is shown that there is a regular increase in metal—carbon force constant in the order Co