What type of isomerism involves the interchange of ions between the inner and outer coordination spheres?

Ionization isomerism is a type of structural isomerism in coordination compounds where the counter ion outside the coordination sphere exchanges places with a ligand inside the coordination sphere. This results in isomers that produce different ions when dissolved in solution.

• A. Ambidentate ligands bonding through different donor atoms: This describes linkage isomerism, where a ligand can bind to the metal through different atoms (e.g., $\text{NO}_2$ vs. ONO).
• B. Different spatial arrangements of the same ligands around the central metal ion: This describes geometric isomerism (e.g., cis-trans isomers) or stereoisomerism.
• C. Redistribution of water molecules in the crystal lattice: This describes hydrate isomerism (a specific type of solvation isomerism), where water molecules can be either coordinated to the metal or present as lattice water.
• D. Interchange of ions between the inner coordination sphere and the outer coordination sphere: This accurately describes ionization isomerism, where an ion from the outer sphere (counter ion) swaps with a ligand from the inner sphere (coordinated to the metal).

The final answer is $\boxed{\text{D. interchange of ions between the inner coordination sphere and the outer coordination sphere}}$