chelating ligands  [ENDORSED]

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Matthew Chan 1B
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chelating ligands

Postby Matthew Chan 1B » Sat Nov 30, 2019 3:41 am

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

Chem_Mod
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Re: chelating ligands  [ENDORSED]

Postby Chem_Mod » Sat Nov 30, 2019 11:01 am

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
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Re: chelating ligands

Postby chari_maya 3B » Tue Dec 03, 2019 8:43 pm

How do you draw diethylenetriammine chelating?

Elizabeth Harty 1A
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Re: chelating ligands

Postby Elizabeth Harty 1A » Sat Dec 07, 2019 11:52 am

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

Matthew Chan 1B
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Re: chelating ligands

Postby Matthew Chan 1B » Sat Dec 07, 2019 1:07 pm

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?

Angela Prince 1J
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Re: chelating ligands

Postby Angela Prince 1J » Sat Dec 07, 2019 6:43 pm

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

chrisleung-2J
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Re: chelating ligands

Postby chrisleung-2J » Sat Dec 07, 2019 8:26 pm

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
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Re: chelating ligands

Postby Nick Lewis 4F » Sat Dec 07, 2019 8:36 pm

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
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Re: chelating ligands

Postby Ashley Nguyen 2L » Sat Dec 07, 2019 9:06 pm

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.

005321227
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Re: chelating ligands

Postby 005321227 » Sat Dec 07, 2019 9:31 pm

sigma bonds are able to rotate already!

Alan Cornejo 1a
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Re: chelating ligands

Postby Alan Cornejo 1a » Sat Dec 07, 2019 9:47 pm

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 .

Adelpha Chan 1B
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Re: chelating ligands

Postby Adelpha Chan 1B » Sat Dec 07, 2019 10:45 pm

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

Kyle Thorin
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Re: chelating ligands

Postby Kyle Thorin » Sun Dec 08, 2019 1:07 am

Sigma bonds have the ability to rotate already.

ATingin_3I
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Re: chelating ligands

Postby ATingin_3I » Sun Dec 08, 2019 2:23 am

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?

Chem_Mod
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Re: chelating ligands

Postby Chem_Mod » Sun Dec 08, 2019 10:22 am

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
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Re: chelating ligands

Postby ASetlur_1G » Sun Dec 08, 2019 11:18 am

Just to clarify, polydentate ligands are chelating right?

Ami_Pant_4G
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Re: chelating ligands

Postby Ami_Pant_4G » Sun Dec 08, 2019 3:46 pm

ASetlur_3I wrote:Just to clarify, polydentate ligands are chelating right?


yes all polydentates are chelating

Natalie Benitez 1E
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Re: chelating ligands

Postby Natalie Benitez 1E » Sun Dec 08, 2019 4:54 pm

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

Chem_Mod
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Re: chelating ligands

Postby Chem_Mod » Sun Dec 08, 2019 5:26 pm

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
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Re: chelating ligands

Postby Kennedi2J » Sun Dec 08, 2019 8:03 pm

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

AnayaArnold_3L
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Re: chelating ligands

Postby AnayaArnold_3L » Sun Dec 08, 2019 9:49 pm

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.

ZevMarx-Kahn3C
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Re: chelating ligands

Postby ZevMarx-Kahn3C » Mon Dec 09, 2019 1:37 am

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

AJForte-2C
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Re: chelating ligands

Postby AJForte-2C » Sun Nov 29, 2020 7:07 pm

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!

905579227
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Re: chelating ligands

Postby 905579227 » Sun Nov 29, 2020 11:21 pm

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.


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