Heme Complex Coordination Compound

[Joey_Okumura_1E]

How do we know the compound is square planar and not tetrahedral? (Does Fe have two lone pairs that cause the compound to be square planar? If so, how would we know this?)
How do we know only one O2 molecule can bind?

[Mackenzie Stockton 2H]

I think we just know that its square planar because Dr. Lavelle told us in class. Otherwise, theres no way to tell if somethings square planar vs tetrahedral if you cant see the Lone pairs.

We know that only one O2 can bind to hemoglobin/the heme complex because the Fe is bonded to 4 N's and a histadine (its Nitrogen Lone pair). So, there is only one more spot for an O2 to bind to make the total coordination number 6.

[Eva Becker]

Hi! When Dr. Lavelle introduced the myoglobin molecule and heme complex to us, he said it was square planar. He did not elaborate on how we know this but from what we've learned about molecular geometries and the heme complex in general, this is my understanding of why it's square planar:
There are 4 Nitrogens (N) forming equatorial bonds to the central atom, Iron (Fe). Above and below the Fe, there's a histidine and an O2 forming axial bonds. Assuming the histidine and the O2 are not bound to the myoglobin/heme complex, we can tell that the formerly octahedral (AX6) molecule now has 2 lone pairs, making it square planar (AX4E2).

[Nancy Yao]

Heme complex is formed when a Fe is bound to a porphyrin ligand, and the porphyrin ligand is a cake-like molecule, a tetra dentate in the shape of square planar with 4 nitrogens.