Ligand Types
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Ligand Types
I still don't really understand the whole mono/di/tri/poly dentate thing. What is the easiest way to identify types of ligands and determine which kind they are based on chemical formulas?
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Re: Ligand Types
Hi Shannon! Mono/di/tri/polydentate refers to the number of regions available on a ligand to bond to a central atom. These are areas with lone pairs, for example. However, I am also confused on how to easily identify ligands and determine their type. I'm assuming drawing out the Lewis structures of these ligands would be the best way to identify electron dense regions and classify them (although this can be a tedious process).
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Re: Ligand Types
I agree with Sasha. Although it may be tedious if, in doubt, I would draw out the Lewis structure and see if there are multiple atoms with lone pairs to bond multiple times.
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Re: Ligand Types
If a ligand only has 1 lone pair, then it clearly can only be monodentate. However, some ligands have multiple lone pairs but are still monodentate. Drawing out the lewis structure helps you determine if a ligand can bind multiple times to the same TM cation. For example, Cl- is surrounded by 4 lone pairs, but once one pair bonds to a TM cation, it wouldn't be possible for the other lone pairs to bond to it - they all point away to minimize repulsion. If you have a ligand w/ a terminal atom that has a lone pair, then some "spacers" like C-H bonds, and then a terminal atom with a lone pair, then the ligand can bend around and bond twice to the same cation. (The spacer c-h bonds are sigma bonds so the molecule can rotate). Another example- The lewis structure may also be a ring - picture benzene and then add NH2 to the top and to the bottom. When this is the case, the lone pairs are directly opposite so the molecule can only bond once to the TM cation - the lone pair on the second N would be pointed directly away.
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