[owk9688]

Hey guys,

In my organometallic book it says that unlike in CO, the lone pair on carbon in an isonitrile ligand is in an antibonding orbital. This doesn't make sense to me, as I've always imagined lone pairs to be in nonbonding orbitals. I've drawn out an MO diagram but I just wind up making the CN (-) as having that carbon lone pair in a nonbonding sp orbital.

Can someone explain how the lone pair in a CNR ligand is in an antibonding orbital?

Thanks!