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chelating ligands

Posted: Sat Nov 30, 2019 3:41 am
by 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.Image

Re: chelating ligands  [ENDORSED]

Posted: Sat Nov 30, 2019 11:01 am
by 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.

Re: chelating ligands

Posted: Tue Dec 03, 2019 8:43 pm
by chari_maya 3B
How do you draw diethylenetriammine chelating?

Re: chelating ligands

Posted: Sat Dec 07, 2019 11:52 am
by Elizabeth Harty 1A
How do you know if there are sigma bonds available for rotation?

Re: chelating ligands

Posted: Sat Dec 07, 2019 1:07 pm
by Matthew Chan 1B
Elizabeth Harty 3A wrote: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?

Re: chelating ligands

Posted: Sat Dec 07, 2019 6:43 pm
by Angela Prince 1J
Elizabeth Harty 3A wrote:How do you know if there are sigma bonds available for rotation?


all sigma bonds can rotate, but pi bonds cannot

Re: chelating ligands

Posted: Sat Dec 07, 2019 8:26 pm
by 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”?

Re: chelating ligands

Posted: Sat Dec 07, 2019 8:36 pm
by 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

Re: chelating ligands

Posted: Sat Dec 07, 2019 9:06 pm
by Ashley Nguyen 2L
Nick Lewis 3D wrote: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.

Re: chelating ligands

Posted: Sat Dec 07, 2019 9:31 pm
by 005321227
sigma bonds are able to rotate already!

Re: chelating ligands

Posted: Sat Dec 07, 2019 9:47 pm
by Alan Cornejo 1a
Angela Prince 3B wrote:
Elizabeth Harty 3A wrote: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 .

Re: chelating ligands

Posted: Sat Dec 07, 2019 10:45 pm
by Adelpha Chan 1B
Elizabeth Harty 3A wrote:How do you know if there are sigma bonds available for rotation?

all sigma bonds able to rotate freely along the axis

Re: chelating ligands

Posted: Sun Dec 08, 2019 1:07 am
by Kyle Thorin
Sigma bonds have the ability to rotate already.

Re: chelating ligands

Posted: Sun Dec 08, 2019 2:23 am
by ATingin_3I
Chem_Mod wrote: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?

Re: chelating ligands

Posted: Sun Dec 08, 2019 10:22 am
by 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

Re: chelating ligands

Posted: Sun Dec 08, 2019 11:18 am
by ASetlur_1G
Just to clarify, polydentate ligands are chelating right?

Re: chelating ligands

Posted: Sun Dec 08, 2019 3:46 pm
by Ami_Pant_4G
ASetlur_3I wrote:Just to clarify, polydentate ligands are chelating right?


yes all polydentates are chelating

Re: chelating ligands

Posted: Sun Dec 08, 2019 4:54 pm
by Natalie Benitez 1E
What exactly is a chelating ligand? Can you also provide an example for it?

Re: chelating ligands

Posted: Sun Dec 08, 2019 5:26 pm
by 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.

Re: chelating ligands

Posted: Sun Dec 08, 2019 8:03 pm
by Kennedi2J
An example would be ethylenediamine (en) which binds to a transition metal at 2 sites.

Re: chelating ligands

Posted: Sun Dec 08, 2019 9:49 pm
by AnayaArnold_3L
Elizabeth Harty 3A wrote: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.

Re: chelating ligands

Posted: Mon Dec 09, 2019 1:37 am
by ZevMarx-Kahn3C
Is this a topic that will be relevant in 14B?

Re: chelating ligands

Posted: Sun Nov 29, 2020 7:07 pm
by AJForte-2C
ZevMarx-Kahn3C wrote: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!

Re: chelating ligands

Posted: Sun Nov 29, 2020 11:21 pm
by 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.

Re: chelating ligands

Posted: Sat Dec 05, 2020 8:25 pm
by Lorena_Morales_1K
Hi!

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

Re: chelating ligands

Posted: Sun Dec 06, 2020 3:41 pm
by Chanel Mao 3D
Lorena_Morales_3D wrote: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!

Re: chelating ligands

Posted: Fri Dec 11, 2020 1:06 pm
by 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 C2O42-, 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 C2O42- 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 :)

Re: chelating ligands

Posted: Sat Dec 12, 2020 6:21 pm
by Renny_kim_2G
Does this mean polydentate ligands and chelating ligands are the same thing?

Re: chelating ligands

Posted: Sat Dec 12, 2020 7:29 pm
by SavannahScriven_1F
Renny_kim_2G wrote: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.

Re: chelating ligands

Posted: Sun Dec 13, 2020 1:38 am
by 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?

Re: chelating ligands

Posted: Tue Dec 15, 2020 5:06 pm
by Moura Girgis 1F
Jessica Hu 3L wrote: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?

Re: chelating ligands

Posted: Wed Dec 16, 2020 10:17 pm
by Sebastian2I
Are there any exceptions to the atom-spacer-spacer-atom condition for chelation or can this be considered absolute?