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1998
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April
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In the Laboratory
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Synthesis of Some "Cobaloxime" Derivatives: A Demonstration of "Umpolung" in the Reactivity of an Organometallic Complex
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Donald L. Jameson, Joseph J. Grzybowski, Deb E. Hammels, Ronald K. Castellano, Molly E. Hoke, Kimberly Freed, Sean Basquill, Angela Mendel, and William J. Shoemaker
Gettysburg College, Department of Chemistry, Gettysburg, PA 17325-1486
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April 1998
Vol. 75 No. 4
p. 447
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| Abstract |
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This article describes a four-reaction sequence for the synthesis of two organometallic "cobaloxime" derivatives. The concept of "Umpolung" or reversal of reactivity is demonstrated in the preparation of complexes. The complex Co(dmgH)2(4-t-BuPy)Et is formed by the reaction of a cobalt (I) intermediate (cobalt in the role of nucleophile) with ethyl iodide. The complex Co(dmgH)2(4-t-BuPy)Ph is formed by the reaction of PhMgBr with a cobalt (III) intermediate (cobalt in the role of electrophile). All the products contain cobalt in the diamagnetic +3 oxidation state and are readily characterized by proton and carbon NMR. The four reaction sequence may be completed in two 4-hour lab periods. Cobaloximes are well known as model complexes for Vitamin B-12 and the experiment exposes students to aspects of classical coordination chemistry, organometallic chemistry and bioinorganic chemistry. The experiment also illustrates an important reactivity parallel between organic and organometallic chemistry.
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| More Information |
 Citation |
Donald L. Jameson, Joseph J. Grzybowski, Deb E. Hammels, Ronald K. Castellano, Molly E. Hoke, Kimberly Freed, Sean Basquill, Angela Mendel, and William J. Shoemaker. J. Chem. Educ. 1998 75 447.
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Keywords |
Laboratory, Inorganic Chemistry, Coordination Chemistry, Inorganic Synthesis, Organometallics, Transition Elements
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History |
Created:
Last Updated: |
June 25, 1999
June 24, 2005
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| Home > JCE Print > Journal of Chemical Education > Issues >
1998
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April
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447
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