Coordination chemistry originated from the work of Alfred Werner, a Swiss chemist who examined different compounds consisting of cobalt(III) chloride and ammonia. When adding hydrochloric acid, Werner noticed that the ammonia could not be completely removed. He then suggested that ammonia should bind more tightly to the central cobalt ion. However, when aqueous silver nitrate was added, one of the products formed was solid silver chloride. The resulting amount of silver chloride was related to the number of ammonia molecules bound to the cobalt(III) chloride. For example, when silver nitrate was added to CoCl3•6NH3, all three chlorides were converted to silver chloride. When silver nitrate was added to CoCl3•5NH3, only 2 of the 3 chlorides formed silver chloride. When CoCl3•4NH3 was treated with silver nitrate, only one of the three chlorides precipitated as silver chloride. The resulting observations revealed the formation of complex or coordination compounds. In the inner coordination sphere, also called the first sphere, the ligands are directly bonded to the central metal. In the outer coordination sphere, sometimes called the second sphere, other ions are attached to the complex ion. The following table is a summary of Werner's observations: INITIAL COMPOUNDS RESULTING FROM THE ADDITION OF AgNO3CoCl3•6NH3[Co(NH3)6]3+(Cl-)3CoCl3•5NH3 [Co(NH3)5Cl]2+(Cl- )2CoCl3• 4NH3 [Co(NH3)4Cl2]+(Cl-)CoCl3•3NH3 [Co(NH3)3Cl3]A coordination compound or complex forms when a ligand is attached to an acceptor by means of a pair of non-bonding electrons (Rajbir Singh, 2002). Coordination compounds form between a metal ion and a molecule with one or more unshared electron pairs, called ligands. According to (Geoaffrey AL..... middle of article ......o living organisms. Metal complexes play a variety of important roles in biological systems. Many natural enzymes and catalysts that regulate biological processes are metal complexes (metalloenzymes); for example, carboxypeptidase, is an important hydrolytic enzyme in digestion It contains a zinc ion coordinated to several amino acid residues of the protein, another enzyme known as catalase, which is. an important catalyst for the decomposition of hydrogen peroxide, contains iron-porphyrin complexes. In these two cases, the coordinated metal ions are most likely the sites of the catalytic activity. can conclude that coordination compounds affect almost every aspect of life from organisms to daily life. So this means that coordination compounds are very important and without them life does not exist...