How is the iron in heme hybridized?

[L83201]

My Biochemistry teacher said it was a sp2d hybridization, then I read somewhere it was a sp2d3 hybridization instead.

I know there are six coordination bonds, but which kinds of orbitals are part of those bonds?

Also, how does the hybridization take place in this case? I'm very confused. If anyone could clarify this, I'd be very grateful. Thanks.

[BabcockHall]

For starters, I suspect that one needs to specify whether we are discussing the iron with or without the oxygen molecule present. I remember looking into this one time and deciding that the answer might be more complicated than I thought it was because not all six ligands are identical.

[L83201]

For starters, I suspect that one needs to specify whether we are discussing the iron with or without the oxygen molecule present. I remember looking into this one time and deciding that the answer might be more complicated than I thought it was because not all six ligands are identical.

 

Yes I also decided the answer was more complicated than I thought. I was talking about the iron with the oxygen molecule present.

[BabcockHall]

I have a 1994 textbook on inorganic biochemistry (Lippard and Berg) that shows the electronic configurations (Figure 11.2). They don't provide the hybridization, however.