How do ligands and coordination complexes work in this case with copper (II) chloride?
When solid $\ce{CuCl2}$ is dissolved in water, aquo complexes are formed.

$\ce{CuCl2_{(s)} + H2O -&gt; [Cu(H2O)6]^2+ + 2 Cl-}$

Addition of ammonia results in a ligand exchange reaction to give tetrammine complexes.

$\ce{[Cu(H2O)6]^2+ + 4 NH3 -&gt; [Cu(NH3)4(H2O)2]^2+ + 2 H2O}$