9C.5 Which of the following ligands can be polydentate? If the ligand can be polydentate, give the maximum number of places on the ligand that can bind simultaneously to a single metal center
How can I tell whether a ligand is monodentate, bidentate, tridentate etc... I'm confused, I know I need to be able to determine whether it has more than one lone pair of electrons at different bonding sites, however, how would I be able to tell whether CO32- is monodentate, bidentate or tridentate?
Polydentate ligands 9C.5 [ENDORSED]
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Re: Polydentate ligands 9C.5
If the ligand has lone pairs on multiple different atoms it is polydentate. H2O has lone pairs on only the oxygen atom, so it is monodentate because it has one binding center. CO3 2- has lone pairs on all of the oxygens so it is polydentate, however, due to its molecular shape it cannot bind to three spots on the central metal atom at the same time, so it can only be bidentate or monodentate.
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Re: Polydentate ligands 9C.5
Lewis structure of (CO3)2-:
-Central C atom that double bonds to one O atom (2 lone pairs)
-C atom forms single bonds with each of the other two O atoms (each has 3 lone pairs)
Because the O atoms that single bond to the C atom have lone pairs they can donate, one of the oxygen atoms or both can form bond(s) with a central metal atom of a coordination complex. Thus, (CO3)2- can be a monodentate or bidentate ligand.
-Central C atom that double bonds to one O atom (2 lone pairs)
-C atom forms single bonds with each of the other two O atoms (each has 3 lone pairs)
Because the O atoms that single bond to the C atom have lone pairs they can donate, one of the oxygen atoms or both can form bond(s) with a central metal atom of a coordination complex. Thus, (CO3)2- can be a monodentate or bidentate ligand.
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Re: Polydentate ligands 9C.5
If you look at the # of lone pairs, you should be able to determine if it's monodentate, bidentate, etc.
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Re: Polydentate ligands 9C.5
I noticed that in b and d, the ion is only able to attach at more than one binding site to the atoms that are attached to the central atom by a single bond and not a double bond. Does this tend to be a trend, and why is that?
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Re: Polydentate ligands 9C.5 [ENDORSED]
While there are 3 oxygens all with lone pairs and available for binding to a metal, it's not possible for all 3 of them to bind simultaneously due to the structure of CO32-. Because of its trigonal planar shape, the large bond angles make it difficult. So, CO32- can only bind one or two sites (potentially) to another metal at once.
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