Which statement is incorrect about CO ligands?

 

 

 

A CO ligand can accept electrons into its π* MO; this weakens the C–O bond

 

In the IR spectrum of Fe(CO)5, absorptions assigned to the CO stretching modes are at higher wavenumber than that of free CO

 

CO ligands can adopt terminal, μ and μ3 bonding modes; the amount of back donation depends on the bonding mode

 

Fluxional behaviour is common in metal carbonyl compounds, and can be investigated by 13C NMR spectroscopy