Nitro vs nitrito linkage isomers

1592 words 7 pages
In this experiment, the nature of linkage isomers will be observed on the example of nitritopentaamminecobalt(III) Chloride and nitropentaamminecobalt(III) Chloride. Their relative stability will be compared on standard conditions and the infrared spectroscopy of both the isomers will be obtained to analyze the characteristic absorption bands for the nitro and nitrito group. Yield for nitritopentamminecobalt(III) Chloride was obtained to be = 1.9221 g(73.24 %) and yield for nitropentamminecobalt(III) Chloride = 0.76 g(76 %)
Linkage isomers may arise when one or more of the ligands can coordinate to the metal ion in more than one way. The first reported example of linkage
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If pH would have been higher, some ammonia could have escaped from the complex, resulting in lower yield and synthesis of the different compound. Nitritopentaamminecobalt(III) Chloride was synthesized first because it is much less stable than the nitro isomer, making it relatively easy to convert nitrito isomer into nitro under normal conditions. If nitrito isomer was synthesized at first, ultraviolet light would have been used to convert nitro isomer into nitrito, which is time-consuming and unnecessary. 2
Synthesis of nitritopentaamminecobalt(III) Chloride was done according to the following reaction :
[CoCl(NH3)5]Cl2 + NaNO2 = [Co(ONO)(NH3)5]Cl2 + NaCl (eqn 1.6)
This is not a redox reaction. It goes to completion under normal conditions with addition of some heating. The yield was