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Chelating Complexes

Posted: Sat Nov 18, 2017 8:13 pm
by Krupa Prajapati
Hi! I was just wondering how exactly we determine if a compound can form chelating complexes. I was having some difficulty with question 17.35, and some guidance would be greatly appreciated!

Re: Chelating Complexes

Posted: Sat Nov 18, 2017 10:09 pm
by Tanaisha Italia 1B
I think chelating complexes can be formed if ligands have lone pairs of electrons which they can use to form additional bonds with a metal ion. In 17.35, nitrogen has a lone pair left after bonding to the complex and the two hydrogen atoms (3 bonds, one lone pair). Therefore, this lone pair could be swapped with a bond to the metal ion, to form a chelating complex, but only if both NH2 molecules could bond to the same metal ion. This would only be possible if both NH2 atoms were on the same side and were reasonable close to one another. Therefore, the answer is b.

Re: Chelating Complexes

Posted: Sat Nov 18, 2017 10:45 pm
by 905022356
Chelating complexes are, in oder words, polydentate ligands. The lone pairs that will form the coordinate bonds must be at the right distance from one another so that they can both bond to the TM cation. The Ideal distance is two atoms in between the lone pairs for linear complexes. However, in the structure given in (b), given that diaminobenzene is chiral, I believe the lone pairs are far enough to form a chelate complex.

Re: Chelating Complexes

Posted: Sun Nov 19, 2017 9:14 am
by Michael Cheng 1C
I'm still confused as to the definition or function of a chelate is versus a regular ligand. What is the distinction between the two?

Re: Chelating Complexes

Posted: Mon Nov 20, 2017 9:57 am
by Yashaswi Dis 1K
@Michael

So a chelate is, by definition from the textbook: "A complex containing one or more ligands that form a ring of atoms that includes the central metal atom. " Basically a chelate is like a name for a type of structure where a ring of ligands are attached to the central metal atom.

vs.

A ligand, by defn. from the textbook: "Lewis base that attaches to the central atom/ion in a d-metal complex." It's basically an individual name for molecules that attach to the central atom, like (OH2) or NH3 for example.

Hope this helps!

-Yashwi

Re: Chelating Complexes

Posted: Mon Nov 20, 2017 2:58 pm
by Isa Samad 1L
So basically a chelating complex is one that forms a ring around a central transition metal. Therefore, the positions of the ligands matter as the coordination covalent bond formed must be in a ring orientation.