Systematic Name of Coordination Compound

Question

Give the systematic name of this coordination compound. Omit -N or -κN type designations.

(NH4)3[Co(NO2)6]

I am posting this at 9:50 PM. This is due by 9:00 AM tomorrow exactly. So I'd need it beforehand so I have time to type in my answer. I have emailed and emailed all day and yesterday for help from my professor but she never responded.

Answer 1

Find the charge on the NO2 ligand by putting the electrons from the bond between Co and N onto N as a lone pair. When you do this, you see that the NO2 ligand has a “-1” charge. There are 6 of these NO2- ligands, and each has -1 charge, so you get -6 from these ligands. If you draw out Lewis dot structure for NH4, you’ll see that each NH4 has a “+1” charge. There are 3 NH4s, so this adds up to +3. So far we are at -6 + 3 = -3. The overall charge on this compound must be zero, as there is no charge listed on the compound. So Co must be +3 to balance out this -3. Now that we know the charge on Co (+3), we can name the compound. NH4+ is called ammonium, and NO2- is called a nitro. There will be a Roman numeral III after the name because cobalt is +3. There is a “hex” prefix before the nitro because there are 6 nitro ligands:

Ammonium hexanitrocobaltate (III)