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 13 C isotopic enrichment and of hydridoirontricobalt dodecacarbonyl. Calculation of CO stretching force and interaction constants

Based on 13 C‐enriched spectra the assignment of the terminal CO stretching bands of Co 4 (CO) 12 , Rh 4 (CO) 12 , and HFeCo 3 (CO) 12 is presented. This corresponds in all three cases to the scheme A 1 > A 1 > E > E > A 1 > E . For the calculation of the ‘non‐rigorous’ CO stretching force and interaction constants a parametric method is described. On the basis of the extremely low CO stretching force constant of the ligands bonded to the iron atom in HFeCo 3 (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 Co 3 plane.