Would a coordination complex form between an ammonium salt and copper (II)?

Answer 1

First off, it depends on the anion of the ammonium salt. That anion might form a coordination compound, complex ion, with copper.

Second, I think that you are asking about the ammonium ion. The answer is no. NH3 forms a coordination compound with copper sulfate, tetramminecopper(II) sulfate. One can actually crystallize this salt out and isolate it. But it decomposes over time. The coordination sphere of copper is labile, not stabile.