Metal ions have a central structural and functional role in many molecular systems, including catalysts, supramolecular assemblies, and biomolecules. Due to their relevance, much work has been done to investigate the structure, kinetics, and thermodynamic stability of metal complexes in solution, including the dynamics of metal-ligand exchange reactions. Using a variety of experimental techniques, including X-ray absorption spectroscopy, neutron scattering and nuclear magnetic resonance (NMR) spectroscopy, several mechanisms have been proposed to describe ligand exchange in the first coordination shell of the metal ion. These mechanisms range from dissociative (D), involving an intermediate of lower coordination number, to associative (A), proceeding through an intermediate of higher coordination number. However, these are extreme cases -in most instances, no such idealised intermediate exists, and instead, a concerted interchange mechanism with dissociative (I d ) or associate (I a ) characteristics occurs. Of particular interest is ligand exchange with solvent, with metal aqua complexes being the most extensively studied. The rate of this exchange depends on the nature of the metal ion, particularly ionic radii, charge, and coordination environment, ranging from 200 ps for Cs + to 300 years for Ir 3+ . Coordination with nonaqueous solvents such as alcohols, dimethyl sulfoxide (DMSO), acetonitrile (MeCN), and amides, has also been explored. Among the cations investigated, significant efforts have been made to study Mg 2+ complexes due to their prominent role in biology, including RNA folding, ATP hydrolysis, cellular signalling, and photosynthesis. In aqueous solution, Mg 2+ forms octahedral [Mg(H 2 O) 6 ] 2+ complexes with a Mg-O distance of 2.10 Å, surrounded by a second solvation shell of 12 water molecules. Water molecules in the first solvation shell are tightly bound to the cation and undergo exchange with the bulk solvent molecules on the microsecond timescale (k = 5.3 ×10 5 s -1 at 298 K) via a dissociative or interchange-dissociative mechanism. Another important example is Pd 2+ , which although less prevalent in biology has an irreplaceable role in organocatalysis and supramolecular chemistry. Pd 2+ complexes have a square planar geometry defined by four coordinate bonds in equatorial positions. The complex can additionally interact with two more loosely bound ligands at the axial positions.