Consider the complex formed between myoglobin and CO. Which of the following correctly describes this substance?

Question

Consider the complex formed between myoglobin and CO.  Which of the following correctly describes this substance?

Quizplus · Accepted Answer

The complex formed between myoglobin and CO is a coordination complex where Fe(II) is coordinated by four atoms: the nitrogen atoms from the imidazole groups of two histidine residues in myoglobin and the carbon and oxygen atoms of CO. Because Fe(II) has six d electrons, four of those electrons are involved in the coordination bond formation. Therefore, Fe(II) has only two unpaired d electrons left, which causes it to follow the 18-electron rule where the total number of electrons in the metal-ligand complex should be close to 18. There are no four coordinate covalent bonds in the structure; instead, the bonds are coordinate covalent bonds formed between the Fe(II) center and the ligands. Therefore, choice A and B are both incorrect for this substance.

Consider the Complex Formed Between Myoglobin and CO