Vibrational frequency shifts for isotopes of hexacarbonylchromium

Carbonyl stretching frequencies and calculated force constants for some isotopic species of Cr(CO)6 in CCl4 solution are tabulated. It is pointed out that force constants calculated from the stretching frequencies for 13C-substituted species are useful for assigning isotopic frequency shifts for the 13C isotope alone, but frequencies for the 18O isotopic shifts show that there are serious limitations to the CO-factored force field