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Synthesis of Some "Cobaloxime" Derivatives: A Demonstration of "Umpolung" in the Reactivity of an Organometallic Complex
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Abstract
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.
Keywords (Audience):
Upper-Division UndergraduateKeywords (Domain):
Laboratory InstructionKeywords (Pedagogy):
Hands-On Learning / ManipulativesKeywords (Subject):
Coordination CompoundsCiting Articles
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This article has been cited by 3 ACS Journal articles (3 most recent appear below).
Syntheses and Characterization of Organo-Group 14 Cobaloxime Compounds
Alan M. Stolzenberg, Sarah R. Workman, Jessica E. Gutshall, Jeffrey L. Petersen, and Novruz AkhmedovInorganic Chemistry2007 46 (16), 6744-6754Syntheses and Characterization of Organo-Group 14 Cobaloxime Compounds
Alan M. Stolzenberg, Sarah R. Workman, Jessica E. Gutshall, Jeffrey L. Petersen, and Novruz AkhmedovInorganic Chemistry2007 46 (16), 6744-6754Metalmetal-bonded cobaloxime complexes (4-t-BuPy)Co(DH)2EPh3 (E = Sn and Pb) were synthesized by reaction of a cobaloxime(I) anion with Ph3ECl and were characterized by X-ray crystallography and NMR spectroscopy. Analogous metalmetal-bonded complexes ...
Synthesis of a Clathrochelate Complex with an Appended Pyridine and Its Coordination to a Cobaloxime Complex
Chaiwat Engtrakul, William J. Shoemaker, and Joseph J. Grzybowski, Ilia Guzei and Arnold RheingoldInorganic Chemistry2000 39 (22), 5161-5163Synthesis of a Clathrochelate Complex with an Appended Pyridine and Its Coordination to a Cobaloxime Complex
Chaiwat Engtrakul, William J. Shoemaker, and Joseph J. Grzybowski, Ilia Guzei and Arnold RheingoldInorganic Chemistry2000 39 (22), 5161-5163An iron clathrochelate complex with an appended pyridyl group is synthesized and characterized. The ability of this complex to act as a ligand is demonstrated via its coordination to cobaloxime complexes. A crystal structure of the clathrochelate complex ...
Nitrogen-15 NMR Study of Solid Cobaloximes Containing 15N-Labeled Pyridine and Aniline
Robert W. Schurko and Roderick E. WasylishenThe Journal of Physical Chemistry A2000 104 (15), 3410-3420Nitrogen-15 NMR Study of Solid Cobaloximes Containing 15N-Labeled Pyridine and Aniline
Robert W. Schurko and Roderick E. WasylishenThe Journal of Physical Chemistry A2000 104 (15), 3410-3420Solid-state 15N NMR spectra of spinning and stationary samples of four cobaloximes containing either pyridine-15N or aniline-15N as ligands are presented. The cobaloximes investigated are pyCo(DH)2Cl (1), pyCo(DH)2Br (2), pyCo(DH)2CH3 (3), and anilCo(DH)2...
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- Received: August 03, 2009
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