Lab Report exp18

Lab Report exp18 - Ryan Cohen 4/12/09 Synthesis of...

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Ryan Cohen 4/12/09 Synthesis of Transition Metal Coordination Complexes The purpose of the lab was to explore the intricacies of transition metal coordination complexes; specifically, in order to synthesize and distinguish isomers of a certain complex. First the lab produced hexaaminecobalt(III) chloride and pentaamminechlorocobalt(III) chloride complexes, which although similar in structure, displayed significant differences due to differences in the crystal field splitting of each complex. The lab then synthesized two isomers of the same coordinating complex, trans-[Co(en) 2 Cl 2 ]Cl and cis-[Co(en) 2 Cl 2 ]Cl; comparing the two isomers, showed the importance of understanding coordination chemistry in order to distinguish and separate isomers of the same complex. The first part of the lab synthesized Hexaaminecobalt(III) chloride,[Co(NH 3 ) 6 ]Cl 3 , demonstrating the chemical properties associated with a strong-field ligand on a metal ion. A sample of CoCl 2 6H 2 O was mixed with ammonium chloride, ammonium hydroxide, and peroxide. Charcoal was added as a catalyst to speed up the reaction. The corresponding chemical equation went as follows: 2CoCl 2 6H 2 O(s) + 2NH 4 Cl(s) + 10NH 3 (aq) +H 2 O 2 (aq) 2[Co(NH 3 ) 6 ]Cl 3 (s) + 14H 2 O(l) As the solution reacted it produced a slightly yellow/brown color. The resulting solution was filtered in order to isolate the [Co(NH 3 ) 6 ]Cl 3 complex. Finally, the precipitate was analyzed under a spectrophotometer. The mass of [Co(NH 3 ) 6 ]Cl 3 produced was .265g giving a relatively low % yield of 21.4%. This could have been due to the difficulty of collecting all of the precipitate from the vacuum filter. The absorption spectrum produced a relatively high absorption rate with a maximum absorption at 1.698A. The data reinforced crucial
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characteristics of the [Co(NH 3 ) 6 ]Cl 3 complex . A high absorption spectrum suggested high energy from the complex. Higher energy produced strong ligand field strength and greater crystal field splitting in the electrons of the d-orbitals of the metal ion. Intuitively, this was seen in the color of the color of the complex, yellow having a relatively high energy in light. Since NH
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This note was uploaded on 05/17/2011 for the course CHEM 1AL taught by Professor Hooker during the Spring '07 term at UCSB.

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Lab Report exp18 - Ryan Cohen 4/12/09 Synthesis of...

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