heme complex chelating?

[Brian Tangsombatvisit 1C]

Is the porphyrin ligand bound to Fe, which forms a heme complex, chelating? Do we also need to know the shape of myooglobin, which is octahedral? But the shape of the heme complex is square planar..

[Adam Kramer 1A]

I believe the porphyrin ligand is chelating because it is polydentate. As for the shapes, I do not know if we need to know that or not.

[805291863]

The porphyrin ligand in polydentate (tetradentate, to be specific), making myoglobin a chelating complex.

As to the shape of myoglobin, I believe we do not need to know its shape. However, the "marshmallow" practice problems included a question on the shape of the heme complex. In the review session, they mentioned that either tetrahedral or square planar would have been acceptable answers.

[Megan_1F]

The ligand to Fe is a tetra dente because it binds to iron at 4 different sites, but is a single ligand.

When O2 attaches to the heme complex, it becomes myoglobin. I do not think we need to know the structure of myoglobin, probably just the structure of the heme complex.

The heme complex is tetrahedral because it has 4 binding sites to the tetradente.