Polydentate vs Monodentate

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Brendan Duong 1I
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Joined: Wed Sep 30, 2020 10:07 pm

Polydentate vs Monodentate

Postby Brendan Duong 1I » Mon Dec 07, 2020 11:26 am

Hi. I'm still confused on how to distinguish a polydentate ligand from a monodentate ligand, and how to tell how many total binding sites it has. Can someone help me?

Arieanne De Guzman 2J
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Re: Polydentate vs Monodentate

Postby Arieanne De Guzman 2J » Mon Dec 07, 2020 11:45 am

A polydentate ligand will have more than one binding site/more than one atom that can donate their lone pair.
A monodentate ligand will have one binding site/one atom that can donate their lone pair.
Drawing the lewis structure can help you see which atoms have a lone pair and then you can distinguish if a ligand is polydentate or monodentate! Hope this helps (:

Samiha Molla 3G
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Re: Polydentate vs Monodentate

Postby Samiha Molla 3G » Mon Dec 07, 2020 11:47 am

For me the best way to tell is by drawing out the Lewis Structure. If there are multiple available lone pairs that could act as bonding sites, then it would be polydentate; if there's only one set of available lone pair electrons then it would be monodentate. Hope that helps!

Samantha Pedersen 2K
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Re: Polydentate vs Monodentate

Postby Samantha Pedersen 2K » Mon Dec 07, 2020 11:57 am

Polydentate ligands must have at least 2 lone pairs available to be donated and typically 1-2 spacer atoms between the atoms with the lone pairs to be donated. The atoms with the lone pairs and the spacer atoms are also usually connected by sigma/single bonds so that the ligand can rotate to orient the two atoms with the lone pairs to be on the same side. As other people have mentioned, it really helps to draw out the Lewis structure to determine if the ligand meets these criteria!

Emmeline Phu 1G
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Re: Polydentate vs Monodentate

Postby Emmeline Phu 1G » Mon Dec 07, 2020 12:01 pm

Hi! A polydentate ligand is a ligand that has more than one binding site (atoms with a lone pair). If it can only bind at one site then it would be considered a monodentate ligand. For me, the best way to distinguish between the both is to look for multiple O, N, or other atoms they act as lewis bases and have an extra lone pair to donate allowing for more bonds to be formed for that specific ligand. Common polydentate ligands would be (en) and oxalate. Hope this helps! :)


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