an introduction to the chemistry of chromium ethan englund augustana college 05.10.02
TRANSCRIPT
An Introduction to the An Introduction to the Chemistry of ChromiumChemistry of Chromium
Ethan EnglundEthan Englund
Augustana CollegeAugustana College
05.10.0205.10.02
Chromium ChemistryChromium Chemistry
• Chromium - Comes form the Greek Chromium - Comes form the Greek word “chroma” meaning colored.word “chroma” meaning colored.
• First Identified in the PbCrOFirst Identified in the PbCrO4 4
• Multiple Oxidation States Multiple Oxidation States
Cr(Acac)Cr(Acac)33
• Full Name is Full Name is Chromium Chromium AcetylacetonateAcetylacetonate
• Octahedral Octahedral Complex of Cr IIIComplex of Cr III
• Optically ActiveOptically Active
Chromium Acac SynthesisChromium Acac Synthesis
• Acetylacetone is added to a Acetylacetone is added to a solution containing Cr (III) ions and solution containing Cr (III) ions and urea.urea.
• The solution is heated thoroughly The solution is heated thoroughly for around 1 ~ 2 hours.for around 1 ~ 2 hours.
• Yields a deep red solution with dark Yields a deep red solution with dark red precipitate.red precipitate.
The Ultra Violet Spectrum The Ultra Violet Spectrum of Cr(Acac)of Cr(Acac)33
Chromium d Orbital SplitChromium d Orbital Split
• Cr (III) - Typical dCr (III) - Typical d33 octahedral metal octahedral metal ion.ion.
• Ligand Field Ligand Field Strength Strength Unimportant Unimportant
Visible SpectrumVisible Spectrum
• Obvious ColorObvious Color• D D D Transitions D Transitions• From this, the From this, the
LFSE (LFSE (oo) and B ) and B
can be can be determined.determined.
Interpreting Spectrum Data: Interpreting Spectrum Data: Tunabe - Sugano DiagramTunabe - Sugano Diagram
• From this, one can From this, one can determine the Racah determine the Racah parameter.parameter.
• Also can give the Also can give the Octahedral Splitting Octahedral Splitting EnergyEnergy
Symmetry and Optical Symmetry and Optical ActivityActivity
• DD3 3 SymmetrySymmetry
• Optical activity Optical activity possible because possible because of the of the enantiomers.enantiomers.
• Right Hand Screw Right Hand Screw Vs. Left Hand Vs. Left Hand Screw FormationScrew Formation
Cr(Acac)Cr(Acac)3 3 EnatiomersEnatiomers
The Joys of Computational The Joys of Computational ChemChem
• Above: The Elctrostatic Potential Graphed on Above: The Elctrostatic Potential Graphed on the Electron Density via ZINDO on CAChethe Electron Density via ZINDO on CAChe
Singly and Doubly Singly and Doubly Occupied OrbitalsOccupied Orbitals
• Prediction based on Prediction based on Jaguar: B88 LYPJaguar: B88 LYP
• Some Oddities in the Some Oddities in the PredictionsPredictions
TT2g2g Vs. e Vs. egg Orbitals Orbitals
• Seem to show dSeem to show dxx22--
yy22 orbitals orbitals
• Along with dAlong with dzz22
indicate indicate eegg
Chromium Acetate Chromium Acetate
• Bidentate Acetate Bidentate Acetate LigandsLigands
• Metal-Metal BondMetal-Metal Bond• Computational Computational
methods and methods and approaches approaches
The Formation of a Delta The Formation of a Delta Bond in a Cr(II) ComplexBond in a Cr(II) Complex
• Commonly Commonly referred to as a referred to as a quadruple bond.quadruple bond.
• Has 8 available Has 8 available valence electronsvalence electrons
• Bond Order of 4Bond Order of 4
Orbital View of the Orbital View of the Quadruple BondQuadruple Bond
• The d orbitals of the delta bondThe d orbitals of the delta bond
• ddxx22--yy22 orbitals occupied M-L bonds orbitals occupied M-L bonds
Conclusion Conclusion
• Transition Metal Computational Transition Metal Computational Work Continues to Gain InterestWork Continues to Gain Interest
• The Chromium Chemistry The Chromium Chemistry described shows a lot of described shows a lot of generalities in transition metal generalities in transition metal chemistry chemistry
BibliographyBibliography
• Atkins, Shriver. Atkins, Shriver. Inorganic Chemistry: Third EditionInorganic Chemistry: Third Edition. Freeman . Freeman and Company N.Y. 1999and Company N.Y. 1999
• Gray, Swanson, Crawford. Gray, Swanson, Crawford. Project ACAC: An Experimental Project ACAC: An Experimental Investigation In Synthesis and StructureInvestigation In Synthesis and Structure. Bogden and Quigley . Bogden and Quigley Inc. Belmont, Ca. 1972Inc. Belmont, Ca. 1972
Appreciation goes out to…Appreciation goes out to…
• Dr. Viste for his invaluable Dr. Viste for his invaluable Quantum/Computational adviseQuantum/Computational advise
• Dr. Lindbeck for her guidance in advanced Dr. Lindbeck for her guidance in advanced inorganic chemistryinorganic chemistry
• Augustana CollegeAugustana College