chelating ligands [ENDORSED]

[Matthew Chan 1B]

How would you determine whether a ligand can bind at multiple sites (or be chelating?) Is there a certain angle threshold? For example like in 9C.7 (I've attached an image of the isomers of diaminobenzene that the book uses). Note that B and C should be switched around to represent what the textbook actually depicts. I just got this image from google.

[Chem_Mod]

As discussed in class, a chelating ligand has more than one bond to the same transition metal cation.

I also discussed in class that the best chelating binding structure/motif was:

atom with lone pair --- spacer atom --- spacer atom --- atom with lone pair
***And the ligand must have sigma bonds to allow rotation and therefore correct positioning of the lone pair atoms to bind to the same transition metal cation.***

I pointed out several chelating examples of this:
ethylenediamine
diethylenetriamine
EDTA

In the diagram above, all the ligands are rigid planar structures.
Ligand A has the N atoms pointing away from each other.
Ligand B, the N atoms are still pointing too far away from each other to bind to the same transition metal cation.

Only ligand C has the structure I discussed in class:

atom with lone pair --- spacer atom --- spacer atom --- atom with lone pair

Since the structure is planar, the N atoms, each with a lone pair, are already in the correct position and therefore do not need to rotate.
Therefore ligand C is the answer.

[chari_maya 3B]

How do you draw diethylenetriammine chelating?

[Elizabeth Harty 1A]

How do you know if there are sigma bonds available for rotation?

[Matthew Chan 1B]

How do you know if there are sigma bonds available for rotation?

dont sigma bonds already have the ability to rotate? so if its just a single sigma bond then it can rotate but if theres pi bonds then you cant rotate. did i answer your question?

[Angela Prince 1J]

How do you know if there are sigma bonds available for rotation?

all sigma bonds can rotate, but pi bonds cannot

[chrisleung-2J]

Would it be correct, then, to say that “Ligand C is capable of chelating due to its atoms with lone pairs having an Ortho arrangement”?

[Nick Lewis 4F]

Does anyone know what Dr. Lavelle means when he says:
atom with lone pair --- spacer atom --- spacer atom --- atom with lone pair
The only part i dont understand is spacer atom. What does spacer atom mean? Conceptually I see why C is the correct answer i am just unfamiliar with this terminology

[Ashley Nguyen 2L]

Does anyone know what Dr. Lavelle means when he says:
atom with lone pair --- spacer atom --- spacer atom --- atom with lone pair
The only part i dont understand is spacer atom. What does spacer atom mean? Conceptually I see why C is the correct answer i am just unfamiliar with this terminology

Spacer atom refers to the two carbons in the benzene that are connecting the amine groups.

[005321227]

sigma bonds are able to rotate already!

[Alan Cornejo 1a]

How do you know if there are sigma bonds available for rotation?

all sigma bonds can rotate, but pi bonds cannot

Thank you for the clarification .

[Adelpha Chan 1B]

How do you know if there are sigma bonds available for rotation?

all sigma bonds able to rotate freely along the axis

[Kyle Thorin]

Sigma bonds have the ability to rotate already.

[ATingin_3I]

As discussed in class, a chelating ligand has more than one bond to the same transition metal cation.

I also discussed in class that the best chelating binding structure/motif was:

atom with lone pair --- spacer atom --- spacer atom --- atom with lone pair
***And the ligand must have sigma bonds to allow rotation and therefore correct positioning of the lone pair atoms to bind to the same transition metal cation.***

I pointed out several chelating examples of this:
ethylenediamine
diethylenetriamine
EDTA

In the diagram above, all the ligands are rigid planar structures.
Ligand A has the N atoms pointing away from each other.
Ligand B, the N atoms are still pointing too far away from each other to bind to the same transition metal cation.

Only ligand C has the structure I discussed in class:

atom with lone pair --- spacer atom --- spacer atom --- atom with lone pair

Since the structure is planar, the N atoms, each with a lone pair, are already in the correct position and therefore do not need to rotate.
Therefore ligand C is the answer.

should we memorize the structure of edta?

[Chem_Mod]

You will not be asked to draw the entire structure of EDTA. However it may be helpful to know which atoms/lone pairs are involved in forming coordinate covalent bonds

[ASetlur_1G]

Just to clarify, polydentate ligands are chelating right?

[Ami_Pant_4G]

Just to clarify, polydentate ligands are chelating right?

yes all polydentates are chelating

[Natalie Benitez 1E]

What exactly is a chelating ligand? Can you also provide an example for it?

[Chem_Mod]

A chelating ligand is a ligand that forms more than one bond to the same transition metal.
Results in a ring of atoms that includes the transition metal atom.

See lecture notes and textbook for multiple examples.

[Kennedi2J]

An example would be ethylenediamine (en) which binds to a transition metal at 2 sites.

[AnayaArnold_3L]

How do you know if there are sigma bonds available for rotation?

Sigma bonds can rotate,but pi bonds can't because of the p-shaped orbitals interlocking side by side.

[ZevMarx-Kahn3C]

Is this a topic that will be relevant in 14B?