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

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Presentation on theme: "An Introduction to the Chemistry of Chromium Ethan Englund Augustana College 05.10.02."— Presentation transcript:

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

2 Chromium Chemistry Chromium - Comes form the Greek word “chroma” meaning colored.Chromium - Comes form the Greek word “chroma” meaning colored. First Identified in the PbCrO 4First Identified in the PbCrO 4 Multiple Oxidation StatesMultiple 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.Acetylacetone is added to a solution containing Cr (III) ions and urea. The solution is heated thoroughly for around 1 ~ 2 hours.The solution is heated thoroughly for around 1 ~ 2 hours. Yields a deep red solution with dark red precipitate.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 d 3 octahedral metal ion. Ligand Field Strength Unimportant

7 Visible Spectrum Obvious ColorObvious Color D  D TransitionsD  D Transitions From this, the LFSE (  o ) and B can be determined.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 D 3 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 T 2g Vs. e g Orbitals Seem to show d x 2 -y 2 orbitals Along with d z 2 indicate e g

14 Chromium Acetate Bidentate Acetate LigandsBidentate Acetate Ligands Metal-Metal BondMetal-Metal Bond Computational methods and approachesComputational methods and approaches

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

16 Orbital View of the Quadruple Bond The d orbitals of the delta bond d x 2 - y 2 orbitals occupied M-L bonds

17 Conclusion Transition Metal Computational Work Continues to Gain InterestTransition Metal Computational Work Continues to Gain Interest The Chromium Chemistry described shows a lot of generalities in transition metal chemistryThe 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. 1999Atkins, Shriver. Inorganic Chemistry: Third Edition. Freeman and Company N.Y Gray, Swanson, Crawford. Project ACAC: An Experimental Investigation In Synthesis and Structure. Bogden and Quigley Inc. Belmont, Ca. 1972Gray, 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 adviseDr. Viste for his invaluable Quantum/Computational advise Dr. Lindbeck for her guidance in advanced inorganic chemistryDr. Lindbeck for her guidance in advanced inorganic chemistry Augustana CollegeAugustana College


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