Question

4) The ion (RUCI(NO)(PPhy)2]* has N-o stretching frequencies at with two co ligands result in frequencies much closer in energy. Provide an au observation. Lo stretching frequencies at 1687 and 1845 cm. Compounds. closer in energy. Provide an explanation for this what does closer in energ

Answer 1

The metal ion can form either triple bond or single bond with nitrogen in NO ligand. Based on this, they have linear and bent geometry respectively.

Since, the vibrational frequency is directly proportional to the square root of force constant, the triple bond in metal-nitrogen vibrates at much higher frequency than single metal-ntrogen bond.

Vibrational frequency of linear molecule (triply bonded metal-ntrogen bond) = 1650 - 1900 cm^-1

Vibrational frequency of bent molecule (singly bonded metal-ntrogen bond) = 1525 -1690 cm^-1.

In case of carbonyl ligand, it forms either single bond or double bond (in case of back bonding) with metal.

When form single bond, it has vibrational frequency = 2143 cm^-1, and when form double bond, its vibrational frequency = 1900 -2100 cm^-1.

From the above two cases it is clear that the difference in vibrational frequency is more in NO as compared to CO.

Frequency is directly proportional to the energy (E = hv

Where E = energy, h = Planck's constant and v = frequency.)

So, the difference in energy is more in NO as Compared to CO ligands.