[Dolphinsiu]

CO and CN-, which is the best pi-acceptor? I choose CN-

Using Molecular Orbital Theory to explain your choice?

                    ___
C             ____   ____                         
               ??   ??          O
                     ??

                    ___
C-           ____   ____                        
                    ??                   N
               ??   ??

I only know the energy level of pi electrons in 2py and 2pz in CN- is lower than that in CO.
But how can I explain CN- is a better pi-acceptor? Please *delete me*

[FeLiXe]

I would say CO

the idea is that the atomic levels of O are much lower than the levels of C. therefore bonding orbitals will be localised at the O and antibonding orbitals at the C. since the antibonding orbital is located at the C, it can easily accept electron density in an M-CO complex.

the difference between the levels in cyanide is not as big. therefore the antibonding orbital is nott as good an acceptor

[Dolphinsiu]

Thanks a lot!Thank you very much for your sharing!

[FeLiXe]

you're welcome

I was worried that it wouldn't be understandable