## Sapling 5

Karina Rodriguez 2H
Posts: 50
Joined: Wed Sep 30, 2020 9:34 pm

### Sapling 5

Can anyone explain how to calculate the coordination number for [Co(en)2(CO)2]Br ? Also what does the (en) refer to?

Nathan Lao 2I
Posts: 88
Joined: Wed Sep 30, 2020 9:40 pm
Been upvoted: 1 time

### Re: Sapling 5

Hi! En refers to the ethylenediamine ligand, C2H4(NH2)2, and is a bidentate ligand. This means that it will bond to the cobalt ion at two sites. Using this information, the two en ligands will make 4 bonds. Add the two CO bonds and you'll get a total of 6 bonds, or a coordination number of 6.

Xinyu Li 1C
Posts: 92
Joined: Wed Sep 30, 2020 9:36 pm

### Re: Sapling 5

(en) refers to NH2CH2CH2NH2, or ethylenediamine. It's a bidentate ligand (coordination number=2). And chlorine is a monodentate ligand (coordination number=1). So together, the coordination number for [Co(en)2(CO)2]Br is 2*2+2*1=6.

Megan Lu 3D
Posts: 90
Joined: Wed Sep 30, 2020 9:49 pm

### Re: Sapling 5

Hi! Like others have explained above, (en) is the ethylenediamine ligand, or NH2CH2CH2NH2 (you can find this in Table 9C.1), which is a bidentate ligand.

To calculate the coordination number, we would consider the number of bonds that the metal (Co) can form with the ligands (en and CO). There are two en ligands, with each forming two bonds, and two CO ligands, with each forming one bond as a monodentate. Thus, we can do 2(2) + 2(1) = 6 total bonds, our coordination number. Hope this helps!

Andrew Yoon 3L
Posts: 92
Joined: Wed Sep 30, 2020 9:36 pm

### Re: Sapling 5

(en) refers to ethylenediamine ligand, or NH2CH2CH2NH2. Ethylenediamine ligand is a bidentate ligand which has a coordination number of 2, and since there are 2 of en, the coordination number would 4. For CO, since there are 2 of it, it will form one ligand each as a monodentate, which will have a coordination number of 2. So in total, the coordination number would be 6.

Thomas Gimeno
Posts: 79
Joined: Wed Sep 30, 2020 9:49 pm

### Re: Sapling 5

En is a ring and contributes 2 to the coordinate number. The cl2 contributes another two to the coordinate number so the total number is 4. This is because the coordinate number is just the number of atoms/molecules the central metal is bound to.

rhettfarmer-3H
Posts: 101
Joined: Wed Sep 30, 2020 9:59 pm

### Re: Sapling 5

yeah for sure, this question is a little tricky in the sense that you have to know you ligands. SO we have 2 different ligands en and we have two of them and we have two CO. For this problem it seems like oh there is simply a coordination number of 4 but wait. En is bidentate so we have to add 2 for each en. SO 4 from the two en and 2 for each monodentate CO. We get a coordination number of 6.