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An Introduction to the Chemistry of Chromium

An Introduction to the Chemistry of Chromium. Ethan Englund Augustana College 05.10.02. Chromium Chemistry. Chromium - Comes form the Greek word “chroma” meaning colored. First Identified in the PbCrO 4 Multiple Oxidation States . Cr(Acac) 3. Full Name is Chromium Acetylacetonate

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An Introduction to the Chemistry of Chromium

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  1. An Introduction to the Chemistry of Chromium Ethan Englund Augustana College 05.10.02

  2. Chromium Chemistry • Chromium - Comes form the Greek word “chroma” meaning colored. • First Identified in the PbCrO4 • Multiple Oxidation States

  3. Cr(Acac)3 • Full Name is Chromium Acetylacetonate • Octahedral Complex of Cr III • Optically Active

  4. Chromium Acac Synthesis • Acetylacetone is added to a solution containing Cr (III) ions and urea. • The solution is heated thoroughly for around 1 ~ 2 hours. • Yields a deep red solution with dark red precipitate.

  5. The Ultra Violet Spectrum of Cr(Acac)3

  6. Chromium d Orbital Split • Cr (III) - Typical d3 octahedral metal ion. • Ligand Field Strength Unimportant

  7. Visible Spectrum • Obvious Color • D  D Transitions • From this, the LFSE (o) and B can be determined.

  8. Interpreting Spectrum Data: Tunabe - Sugano Diagram • From this, one can determine the Racah parameter. • Also can give the Octahedral Splitting Energy

  9. Symmetry and Optical Activity • D3 Symmetry • Optical activity possible because of the enantiomers. • Right Hand Screw Vs. Left Hand Screw Formation

  10. Cr(Acac)3 Enatiomers

  11. The Joys of Computational Chem • Above: The Elctrostatic Potential Graphed on the Electron Density via ZINDO on CAChe

  12. Singly and Doubly Occupied Orbitals Prediction based on Jaguar: B88 LYP Some Oddities in the Predictions

  13. T2g Vs. eg Orbitals • Seem to show dx2-y2 orbitals • Along with dz2 indicate eg

  14. Chromium Acetate • Bidentate Acetate Ligands • Metal-Metal Bond • Computational methods and approaches

  15. The Formation of a Delta Bond in a Cr(II) Complex • Commonly referred to as a quadruple bond. • Has 8 available valence electrons • Bond Order of 4

  16. Orbital View of the Quadruple Bond • The d orbitals of the delta bond • dx2-y2 orbitals occupied M-L bonds

  17. Conclusion • Transition Metal Computational Work Continues to Gain Interest • The Chromium Chemistry described shows a lot of generalities in transition metal chemistry

  18. Bibliography • Atkins, Shriver. Inorganic Chemistry: Third Edition. Freeman and Company N.Y. 1999 • Gray, Swanson, Crawford. Project ACAC: An Experimental Investigation In Synthesis and Structure. Bogden and Quigley Inc. Belmont, Ca. 1972

  19. Appreciation goes out to… • Dr. Viste for his invaluable Quantum/Computational advise • Dr. Lindbeck for her guidance in advanced inorganic chemistry • Augustana College

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