Question

Account for the differences between the solid state and solution spectra of the cluster Co3(µ3-CCO2Me)(CO)9

Solid state:

Solution IR:

BRUKER 2 500 3500 1500 3000 2500 2000 1000 Wavenumber cm-1 Solution IR spectra of Co3(H3-CCO2Me) (CO)9 in petroleum spirit 1001ㅡㅡ 2109 л | 2032 90 1695 80 701 60 2047 50 40 30 2063 cm-1 2200 2000 1800 1600

Answer 1

In the solution IR of the Co₃(µ₃-CCO₂Me)(CO)₉, the IR spectra mainly has been focused on the carbonyl group (CO) stretching frequency. As it is well known that carbonyl group (CO) stretching frequency of the CO use to obtained in the range of 1850-2180 cm^-1 which show the presence of CO group in it. Two prominent carbonyl group (CO) stretching frequency is shown at 2063 and 2047 cm^-1 which is due to two different type of CO groups by position. One weak band at 1695 cm^-1 is due to the C=O ester group stretching.

In the solid IR of the Co₃(µ₃-CCO₂Me)(CO)₉, the full range IR spectra is shown. In which the carbonyl group (CO) stretching frequency is shown in the 2110-19996 cm^-1. In addition to this C-H stretching frequency is also obtained at around 2959 .68 cm^-1 for CH₃ group present in the ligand bridged. One weak band at 1679.66 cm^-1 is due to the C=O ester group stretching.

In the comparison of both the IR spectra, it can be said that in solid IR spectra in comparison to solution IR spectrum the bond stretching frequency is more in care of carbonyl while less for C=O ester group in comparison with the liquid IR.