A new approach to predicting the carbonyl stretching frequencies of Co 2(CO)8 with D3d symmetry

Abstract

This paper describes a method for determining C-O stretching frequencies of dicobalt octacarbonyl belonging to D3d point group. The method is based on the variation of fundamental C-O stretching frequencies and C-O stretching force constants of axially substituted X3MCo(CO) 4 (M=Si, Ge, Sn and Pb; X=Cl, Ph and Et) molecules with the dipole moment of X3M-Co(CO)4 bond. Frequencies of a 1g(1), a2u(2) and eu modes have been evaluated from the graph of frequency versus dipole moment, and the frequencies of a1g(2) and eg modes determined from the equations derived by using the CO-factored force field. The calculated frequencies have been found to be consistent with the experimental values. With the use of the calculated frequencies, the C-O factored force constants of Co2(CO)8 with D3d symmetry have been calculated. In addition, frequencies of mono-13CO substituted species of Co2(CO)8 have been estimated and compared with observed frequencies of the species.