Infrared Spectroscopic Studies on Metal Carbonyl Compounds. Part XIX. Analysis of the terminal CO stretching region of the infrared spectra of tetracobalt and tetrarhodium dodecacarbonyl by 13C isotopic enrichment and of hydridoirontricobalt dodecacarbonyl. Calculation of CO stretching force and interaction constants

Based on 13C‐enriched spectra the assignment of the terminal CO stretching bands of Co4(CO)12, Rh4(CO)12, and HFeCo3(CO)12 is presented. This corresponds in all three cases to the scheme A1 > A1 > E > E > A1 > E. For the calculation of the ‘non‐rigorous’ CO stretching force and interaction constants a parametric method is described. On the basis of the extremely low CO stretching force constant of the ligands bonded to the iron atom in HFeCo3(CO)12 a considerable polarization of the Fe‐H bond in the sense Fe(δ−)––H(δ+) is suggested, and the position of the H‐ligand is supposed ‘in the cage’ near, or on the Co3 plane.