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Polydentate Ligands

Posted: Tue Nov 03, 2015 12:38 pm
by Emily Huang 2A
I had a question about Question 17.33 from the textbook. The questions asks: "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."

For part b) of the question, which proposes CO3^2-, the answer is bidentate. Why isn't this ion tridentate because of the three oxygen atoms?

Re: Polydentate Ligands

Posted: Tue Nov 03, 2015 4:22 pm
by Chem_Mod
Only two of the oxygen atoms will be able to bind because the third has a double bond to the carbon, satisfying its octet. The other two will have a negative charge and will be available for coordination.

Re: Polydentate Ligands

Posted: Thu Nov 12, 2015 5:36 pm
by JuliaPark2H
To Chem-Mod,
Could you explain how something becomes available for coordination?
If the element in a structure has a formal charge not equal to zero, does that mean it is a potential ligand?

I am having trouble identifying polydentates and conceptualizing the idea of chelating.
During office hours, a UA told me that polydentates are certain structures that just need to be memorized as bidentate, tridentate, or hexadentates, but what determines their denticity?

Also, what are the limits of chelating?
As in, is there a specific angular limit of a polydentate for chelating? Since there are numerous ways to draw complex lewis structures, how would we determine if the shapes that we drew allow chelation (or do we just have to consider all of the possible shape/structures)?

I apologize for the excessive questioning...