EDTA+

[Ian_Lee_1E]

Hello, when professor talked about Ethylene - Diamine - Tetra - Acetate, the Ethylene, NH2-CH2-CH2-NH2, can rotate to make a ring, said by professor in his lecture.

Is this related to the ideal bonding geometry of ligand that can form more than one bond to the same TM cation (Chelate)? Where ligands form a ring to the same TM metal?

If it is similar, why can the Ethylene rotate even if there is no transition metal?

[Nicole Huang 3F]

I believe the ethylene rotates because it is a sigma bond that is attaches to the :N (since only a single bond is present), and so sigma bonds can rotate and allow the shape to swing around to form that chelate shape, where the TM connects the two ends of the ligand. This way, the complex has the cations bonded tightly.

[David Chibukhchian 2G]

If I'm not mistaken, the ability to form a ring is basically referencing how chelates form and integrate the central TM cation as a part of it. In addition, I remember that Dr. Lavelle said that these ligands can rotate in this manner because they have single bonds. Single, or sigma, bonds can rotate because their shared electron region is located on the internuclear axis. This means they aren't rigid like pi bonds are. I hope that answers your question!