A textbook question asks: Which of the ligands can be polydentate? If the ligand can be polydentate, give the maximum number of places on the ligand that can bind simultaneously to a single metal center.
I'm a little confused on the process of how you would start to figure this out. Thanks!
Polydentate molecules
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Re: Polydentate molecules
Hi! A polydentate ligand is a ligand that can form more than 1 bond with the central metal atom. This means it has to have at least 2 lone pairs and can have more, and is also dependent on the possible arrangement of the lone pairs relative to the central atom.
To do this, draw a Lewis diagram!
For HN(CH2CH2NH2)2, there will be a central nitrogen and two nitrogens on the outside edges of the molecule. There are lone pairs on each of these nitrogens, meaning it can for 3 bonds with the central atom (tridentate). H20 has two lone pairs on the O, but only one overlap of orbitals will fit in that region (for 2 bonds the repulsion would be too strong) so it makes 1 bond.
For (CO3)2-, consider it's molecular geometry.
Even though each of the O atoms has lone pairs around it, each of the O atoms are 120 degrees apart due to the trigonal planar geometry. Therefore, at most only 2 of the O's will be able to be on the same side and bond to the central metal atom. At other times, the (CO3)2- molecule will only bond once with the central atom just due the molecular geometry. So (CO3)2- can be bidentate, but most times monodentate.
To do this, draw a Lewis diagram!
For HN(CH2CH2NH2)2, there will be a central nitrogen and two nitrogens on the outside edges of the molecule. There are lone pairs on each of these nitrogens, meaning it can for 3 bonds with the central atom (tridentate). H20 has two lone pairs on the O, but only one overlap of orbitals will fit in that region (for 2 bonds the repulsion would be too strong) so it makes 1 bond.
For (CO3)2-, consider it's molecular geometry.
Even though each of the O atoms has lone pairs around it, each of the O atoms are 120 degrees apart due to the trigonal planar geometry. Therefore, at most only 2 of the O's will be able to be on the same side and bond to the central metal atom. At other times, the (CO3)2- molecule will only bond once with the central atom just due the molecular geometry. So (CO3)2- can be bidentate, but most times monodentate.
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