Sapling #5 for Week 9

[Melody Haratian 2J]

Hi guys!
I was doing the sapling HW for week 9 and got stuck on #5. What does the “en” in [Cd(en)Br₂] mean? Also, how would you find the coordination number for this molecule?
Thanks

[Melody Wu 2L]

en is shorthand for the ethylenediamine ligand, which is bidentate. Since Br has one bonding site and there are two of them, plus the two bonding sites on the ethylenediamine ligand, there's a total of 4 bonding sites. Therefore the coordination number would be 4.

[Darlene Lien 3E]

Hi, also, I think Dr. Lavelle posted a worksheet on his website that would help with naming coordination compounds, so definitely check that out! Hope this helps!

[Juliet Cushing_2H]

I got that one wrong too and Sapling popped up saying that en stands for "ethylenediamine" which is a bidentate molecule. Each molecule can bind to the TM twice, so (en)2 will occupy 4 bonding regions! This will help find out the coordination number.

[Scot Widjaja Dis 1J]

en stands for ethlyenediamine and it is a bidentate ligand, meaning it can donate two electron pairs to the central transition metal cation. In other words, it can form two bonds with the metal. Knowing this, and knowing the compound formula is [Cd(en)Br2], we know that the coordination number will be 4, since en forms 2 bonds and each Br forms 1 bond, giving a total of 4 bonds.