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TEXT 9 COORDINATION CHEMISTRY
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COORDINATION CHEMISTRY Complexes or coordination compounds are molecules that posess a metal center that is bound to ligands (atoms, ions, or molecules that donate electrons to the metal). These complexes can be neutral or charged. When the complex is charged, it is stabilized by neighboring counter-ions. Coordination chemistry emerged from the work of Alfred Werner, a Swiss chemist who examined different compounds composed of cobalt (III) chloride and ammonia. Upon the addition of hydrochloric acid, Werner observed that ammonia could not be completely removed. He then proposed that the ammonia must be bound more tightly to the central cobalt ion. However, when aqueous silver nitrate was added, one of the products formed was solid silver chloride. The amount of silver chloride formed was related to the number of ammonia 82 molecules bound to the cobalt (III) chloride. For example, when silver nitrate was added to CoCl 3 ·6NH 3 , all three chlorides were converted to silver chloride. However, when silver nitrate was added to CoCl 3 ·5NH 3 , only 2 of the 3 chlorides formed silver chloride. When CoCl 3 ·4NH 3 was treated with silver nitrate, one of the three chlorides precipitated as silver chloride. The resulting observations suggested the formation of complex or coordination compounds. In the inner coordination sphere, which is also referred to in some texts as the first sphere, ligands are directly bound to the central metal. In the outer coordination sphere, sometimes referred to as the second sphere, other ions are attached to the complex ion. Werner was awarded the Nobel Prize in 1913 for his coordination theory. The following table is a summary of Werner's observations: жүктеу/скачать 4.51 Mb. Достарыңызбен бөлісу:
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