Aquation is the chemical reaction involving "incorporation of one or more integral molecules of water" with or without displacement of other atoms or groups.[1] The term is typically employed to refer to reactions of metal complexes where an anion is displaced by water. For example, bromopentaamminecobalt(III) undergoes the following aquation reaction to give a metal aquo complex:[2]

[Co(NH3)5Br]2+ + H2O → [Co(NH3)5(H2O)]3+ + Br

This aquation reaction is catalyzed both by acid and by base. Acid catalysis involves protonation of the bromide, converting it to a better leaving group. Base hydrolysis proceeds by the SN1cB mechanism, which begins with deprotonation of an ammonia ligand.

See also


  1. ^ IUPAC, Compendium of Chemical Terminology, 2nd ed. (the "Gold Book") (1997). Online corrected version: (2006–) "aquation". doi:10.1351/goldbook.A00426
  2. ^ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.