Infrared Spectrum of CO Chemisorbed on Iron

The infrared spectrum of CO chemisorbed on iron has been obtained in the 270 to 5000 cm—1 range. Two absorptions were found, one at 580 cm—1 and one at 1950 cm—1. From a vibrational analysis of five possible surface complexes, it is concluded that the observed spectra best fits the structure Fe=C=O, where the iron atom is part of the metal lattice. Force constants calculated for the Fe–C and C–O bonds, respectively, are 4.1 and 13.9 md/A. Comparison of these force constants with others suggests that both bonds are approximately double bonds. Use of empirical rules by Pauling and Badger both give an iron carbon bond length of about 1.67 A.