AbstractC—O stretching frequency of inorganic carbonyl molecules is quite characteristic in the vibrational spectroscopy (the IR and Raman). Since such stretching modes are quite different from the skeletal modes, a non‐mechanical coupling model has been proposed by Cotton1). The C—O stretching force constants and their interaction constants may be calculated semiquantitatively from their characteristic frequencies. The trouble is that the number of vibrational frequencies is always less than the number of force constants, whenever a symmetry irreducible representation contains more than one frequency. Cotton suggest that the interaction constants for octahedral type molecule from thedpπ bonding point of view1‐2). Instead of this, a model of maximum interaction between M—C—O bonds is proposed in this paper. Such model not only gives better remedy to the problem of octahedral complexes, but also is useful to solve the normal modes in molecules of trigonal bipyramidal and many othe