Structure of the complex [Cu(NH3)4](ClO4)
The complex [Cu(NH3)4](ClO4) consists of a central copper ion (Cu2+) coordinated to four ammonia (NH3) ligands. The ammonia ligands act as monodentate ligands, meaning they bind to the central copper ion through a single donor atom (nitrogen). The coordination number of the central copper ion is 4, as it is surrounded by four ligands. This forms a tetrahedral geometry around the copper ion.

Structure of [Cu(NH3)4](ClO4) in solution
When [Cu(NH3)4](ClO4) is dissolved in solution, the complex dissociates into its constituent ions. The complex dissociates into Cu2+ ions and four NH3 ligands. The perchlorate ion (ClO4-) remains as a counter ion in the solution.
In solution, the Cu2+ ions are hydrated to form [Cu(H2O)4]2+ complexes, where water molecules replace the ammonia ligands. The coordination number of the central copper ion increases to 6, as it is now surrounded by six ligands (four water molecules and two ammonia molecules). This results in an octahedral geometry around the copper ion.
The interchange of ligands in solution is an example of ligand exchange reactions, where ligands are replaced by other ligands. This phenomenon is commonly observed in coordination chemistry and has implications in various chemical reactions and processes.
Overall, the structure of the complex [Cu(NH3)4](ClO4) changes in solution due to the dissociation and hydration of the central copper ion, leading to the formation of [Cu(H2O)4]2+ complexes with a different coordination geometry.