Reaction with excess NH3

• With excess NH3 ligand exchange reactions occur with Cu and Cr, and their hydroxide precipitates dissolve in excess ammonia
• The ligands NH3 and H2O are similar in size and are uncharged. Ligand exchange occurs without change of co-ordination number for Cr

  • Cr becomes [Cr(NH3 )6 ]3+ purple solution

  This substitution may, however, be incomplete as in the case with Cu

  • Cu becomes [Cu(NH3 )4 (H2O)2 ]2+ deep blue solution