Sapling Homework 9 Problem 2

[Adam_Ventura_1H]

I am having some trouble with this question, which is asking me to classify the coordination compounds according to the coordination number. I know how to do it when the ligands are monodentate, but when they are not it is more difficult. I was wondering what the best way to know if a ligand is not monodentate and how to figure out how many bond sites a ligand has. Any tips would be super helpful. Thanks.

[Joseph Hsing 2C]

If an attached ligand is monodentate then count 1 towards the coordination number for each, and for bidentates count 2 towards the coordination number of the central atom, etc. Hope this helped!

[Keerthana Sundar 1K]

I am having some trouble with this question, which is asking me to classify the coordination compounds according to the coordination number. I know how to do it when the ligands are monodentate, but when they are not it is more difficult. I was wondering what the best way to know if a ligand is not monodentate and how to figure out how many bond sites a ligand has. Any tips would be super helpful. Thanks.

So based on what I received for the question, none of the provided molecules are bidentate. All of them seem to be monodentate. When you determine the coordination number for coordination compounds, you would 1) only look at what is inside the brackets, 2) count how many bonds the central atom has. For example, the molecule K3[CoF6]. Only the formula inside the brackets is the coordination compound we are looking at. In this, we see that Co forms 6 bonds with the F atoms, so the coordination number must be 6.

In the event that a molecule was bidentate, you would know based on the size of the molecule and its Lewis structure. For example, the en molecule, when you draw its Lewis structure, has a carbon chain, and each end of the carbon chain is capped with a nitrogen and 2 hydrogens. Each of the capping nitrogens has a lone pair, so there are two lone pairs on the atom, and they are separated by spacing atoms in between (without spacers, a molecule cannot be bidentate because there is not enough space for both lone pairs to bond). This means that en must be bidentate. Hopefully this helped! Let me know if you want clarification on any of the above topics or have other questions!

[Samantha Low 3D]

Thank you for posting! I had trouble with this problem too and reading all these responses really helped me. It was very helpful for me to draw the ligands out and count the lone pairs to see if they are monodentate or polydentate. The number of lone pairs it has is the number of bond sites it has. While all these ligands were monodentate, this strategy was good practice and helped me visualize what I was working with more clearly. Hope this helps!

[simona_krasnegor_1C]

If an attached ligand is monodentate then count 1 towards the coordination number for each, and for bidentates count 2 towards the coordination number of the central atom, etc. Hope this helped!

This was super helpful because I kept getting questions with bidentrates wrong! Thank you!!

[darchen3G]

To be honest you don't need to do all of that work. All you do is identify the metal inside the brackets, then see how many molecules are attached to it. If it's monodentate add 1, bidentate add 2. That gives the coordination number.

[Neha Gupta 2A]

To figure out if it is monodentate or bidentate it helps to draw the lewis structure so you can see the potential number of potential bond sites.

[Rose_Malki_3G]

use this list https://sites.google.com/site/chempendix/ligands to determine what type the ligand is.

[RitaThomas_3G]

I definitely agree with what has been said previously by other students! However, I think when looking at this specific question, we don't need to overthink it too much. The approach that I found helpful was looking at the molecules that were inside the brackets, not outside. Then, I found how many atoms were bound to the central atom. This number of bonds would then be the coordination number!

[Lorraine Jiang 2C]

Hi! So coordination number is basically the number of ligands bonded to the central transition metal in a complex ion.

Hope it helps!

[Violet Kwan 3H]

I would also agree with the comments above. It would be helpful to just recognize the common ligands and memorize how many binding sites they have. Drawing it out can also help if you are stuck! I think you have the basic ideas down, just know that for bidentates you add 2 (2 binding sites), tridentates you add 3 (3 biding sites), and so on.