What is the IUPAC name of [Co(NH3)6]SO4?

The IUPAC name of the complex \([Co(NH_3)_6]SO_4\) is hexaamminecobalt(II) sulphate.

Here's how the name is derived:

1. Start with the central metal ion: cobalt (Co).
2. Indicate the coordination number in Roman numerals: (II) indicates that cobalt has a +2 oxidation state.
3. Specify the ligands: The ligands in this complex are ammonia (NH₃), and there are six ammonia ligands present. Each ammonia ligand is called "ammine."
4. Write the ligands in alphabetical order followed by their multiplicity (in this case, "hexa" indicates six): hexaammine.
5. Finally, indicate the counterion, which is sulphate (SO₄). Since sulphate is a common anion, its name remains unchanged.

Putting it all together, the IUPAC name of \([Co(NH_3)_6]SO_4\) is hexaamminecobalt(II) sulphate.