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?

[AJForte-2C]

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

I think that it will, but I think this would be more relevant for a biochem/Ochem class. Hope this helps!

[905579227]

Wait I thought that the whole concept of a ligand was a biology term, since when is it in chemestry and what is its definition when it comes to the field of chemistry.

[Lorena_Morales_1K]

Hi!

Perhaps someone else has already asked this but I was wondering, what exactly is a chelating ligand? :(

[Chanel Mao 3D]

Hi!

Perhaps someone else has already asked this but I was wondering, what exactly is a chelating ligand? :(

Hi! Chelating ligands are basically polydentate ligands that can attach to two or more positions to a metal atom. Hope this helps!

[SavannahScriven_1F]

Hi! This is just a clarification statement I wanted to type out to be sure I'm understanding resonance/chelating ligands properly. In today's review session with C₂O₄^2-, it doesn't matter when we draw the 2 Os that share lone pairs opposite one another (a structure that, on paper, looks as if the lone pairs are opposite one another and does not appear able to bond to the same TM) because really the C₂O₄^2- ion has delocalized e-, so each O has an equal ability to form a chelate. Hopefully that makes sense and someone can tell me that I'm thinking about it the right way. Thank you :)

[Renny_kim_2G]

Does this mean polydentate ligands and chelating ligands are the same thing?

[SavannahScriven_1F]

Does this mean polydentate ligands and chelating ligands are the same thing?

not always. A ligand can be polydentate but bind to two different transition metals. The result wouldn't be a ring, so the compound wouldn't be a chelate. A ligand that does this would be called a bridging ligand instead.

[Jessica Hu 3L]

Then to clarify, a ring is what is a chelate? and that forms when it's a ligand-spare atom-spare atom-same ligand?

[Moura Girgis 1F]

Then to clarify, a ring is what is a chelate? and that forms when it's a ligand-spare atom-spare atom-same ligand?

I am also confused on this. Could someone clarify?

[Sebastian2I]

Are there any exceptions to the atom-spacer-spacer-atom condition for chelation or can this be considered absolute?