Question

give the IUPAC name of [Co(en)2(NO3)2]^+

Answer 1

aquachlorobis(ethylenediamine)cobalt(III) dichloride

How I got that:

the metal Co is cobalt.

the ligands are “en” (ethylenediamine), H2O (aqua), and Cl- (chloro)

Put the ligands in alphabetical order, then the metal name: aqua-chloro-ethylenediamine-cobalt

There are two ethylenediamine ligands “(en)2” so use the prefix bis to indicate two of them (not di, since “ethylenediamine” already contains a numerical prefix).

So we have aquachlorobis(ethylenediamine)cobalt…

The oxidation number of cobalt is +3, so use the Stock number (III), which is the corresponding Roman numeral.

The overall charge of the complex is +2: positive, so do not add “ate” to the metal name.

Then, using the name of the complex cation, name the ionic compound: aquachlorobis(ethylenediamine)cobalt(III) dichloride. The “di” in “dichloride” is not strictly necessary, since (as in calcium chloride) it is implied by the charge of the cation.