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?

[Aaron Kwan 3B]

How many similar bonds to these ^ can be created?

[Tony Chen 1F]

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

Remember that a chelate must have ligands that form a ring-like structure around the central atom

[Jacqueline Musico 3A]

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

The spacer atoms are atoms that do not have lone pairs. There must be exactly two of these "regular" atoms in between two atoms that each have a lone pair. This "formula" will allow the ligand to be chelating or bind in multiple places on the metal cation, so a ring structure is formed.

[405566265]

Is there a limit to how many ligands can be in a compound ? Or if there is one molecule that is a ligand can there be another cation acting as one as well?

[Gianna Greco 1G]

I think that six is the maximum number of ligands because electron pairs repel each other and can't really form a bond angle less than 90 degrees. However, I am not sure if our textbook just does not go into whether it is possible to have more than 6 but I think for now that is all we have to recognize.

[305692127]

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

Remember that a chelate must have ligands that form a ring-like structure around the central atom

Polydentate ligands are range in the number of atoms used to bond to a central metal atom or ion. Meanwhile Chelating ligands are attached to a central metal ion by bonds that are from two or more donor atoms. So no they are not the same thing.

[305692127]

Is there a limit to how many ligands can be in a compound ? Or if there is one molecule that is a ligand can there be another cation acting as one as well?

There is a limit to how many ligands can be in a compound and it is 6. If there is a molecule that acts like a ligand then there can be another acting as a cation.

[Morgan Micallef 1A]

Sigma bonds can rotate, pi bonds can't!

[chemoyku dis 1B]

Hi!

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

Hi!

a ligand is a neutral molecule or an ion that binds to a central metal atom to form complex coordination compounds. They are lewis bases because they contain at least one pair of electrons to donate to the central metal atom. A chelating ligand is a polydentate ligand meaning that it has more than one donor site (lone pair) and it forms a ring structure with the central metal ion.

[Levon_Avedian_2H]

What are some examples of chelating ligands and their bond angles?

[Levon_Avedian_2H]

How do Sigma bonds relate with chelating ligands?

[505801516]

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

pi bonds don't/can't rotate, but sigma bonds can.

[Grace M Miller 1K]

What are some examples of chelating ligands and their bond angles?

Common textbook examples: Hemoglobin, chlorophyll, Oxalic acid, EDTA

[Shubhreet Bhullar 3C]

Hi, So a chelating ligand is a ligand that has two or three coordination sites allowing for the formation of a ring-link structure. Some examples of chelating ligands include: Chlorophyll, EDTA (Ethylenediamine tetraacetate) ,hemoglobin, Oxalic acid, and various other less common ones.

[Julianne_Sue_3A]

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

Not quite. We can think of chelating ligands as a sort of subset of polydentate ligands because we know that it must bind more than once to the same metal atom. For example, Hemoglobin (protein+iron complex), pictured below, exemplifies this and you can clearly see the ring structure.

On the other hand, a polydentate ligand doesn't ligate to the same metal atom, so it isn't always chelating.

[Catherine K 2B]

Pi bonds cannot rotate, but all sigma bonds can

[505801516]

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

pi bonds are the bonds that are not able to rotate, but sigma bonds do have that ability

[LianaHernandez1F]

For these type of problems do we need to label all different types of bonds or does it not have to do with that necessarily?

[306060519]

You need to utilize the overall translation system method you learned in math

[Sandra Espinoza 3A]

For these type of problems do we need to label all different types of bonds or does it not have to do with that necessarily?

To answer your question, I am sure that is we need to know a bond then we will have to write it down and identify the bond as it will help us answer the question.