Coordination chemistry arose from the work of Alfred Werner, a Swiss chemist who examined several compounds consisting of cobalt(III) chloride and ammonia. When hydrochloric acid was added, 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 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 internal 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 COMPOUND RESULT COMPOUNDS AFTER ADDING 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 is formed when a ligand is attached to an acceptor by means of a lone pair of electrons (Rajbir Singh, 2002). Coordination compounds form between a metal ion and a molecule with one or more unshared electron pairs, called a ligand. According to (Geoaffrey AL..... middle of paper ......or living organisms. Metal complexes play a variety of important roles in biological systems. Many enzymes and natural catalysts that regulate biological processes are metal complexes ( metalloenzymes ); for example, carboxypeptidase, is a hydrolytic enzyme important 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 complexes. iron-porphyrin. In both of these cases, coordinated metal ions are most likely the sites of catalytic activity. From the above research, it can be concluded that coordination compounds affect almost all aspects of life, from organisms to daily life. This therefore means that coordination compounds are very important and without them life practically does not exist.