Both N2 and CO are considered sigma-donor and pi-acceptor. Their MO diagram is similar, so I wonder why CO binds generally more strongly and it is a more common ligand.
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$\begingroup$ related chemistry.stackexchange.com/questions/93797/… $\endgroup$ – Mithoron Aug 1 '19 at 22:45
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2$\begingroup$ Both the sigma HOMO and the pi LUMO of CO are polarised towards carbon - so the overlap with metal orbitals is much better $\endgroup$ – orthocresol♦ Aug 1 '19 at 22:58
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$\begingroup$ I saw the link and the other question doesn't have an answer jet. I saw they asked about N2 and O2, I think it is a different explanation because N2 and O2 have very different MO instead N2 and CO are very similar $\endgroup$ – C.X.F. Aug 1 '19 at 22:59
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$\begingroup$ @orthocresol - do you mean that is because CO is polar? (2 different atoms) $\endgroup$ – C.X.F. Aug 1 '19 at 23:01
