problem set 5 key - Chemistry 312 Problem Set 5 (due...

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Chemistry 312 Problem Set 5 (due Friday, August 5) 1. I stated in lecture that, for octahedral symmetry molecules, the ligand atom p orbitals oriented perpendicular to the metal-ligand bond would belong to the symmetry species T 1g , T 1u , T 2g , and T 2u . Using drawings or reducible representations, show that this is the case. You will have to choose your phases wisely. Using reducible representations: O h E 8 C 3 6 C 2 6 C 4 3 C 2 i 6 S 4 8 S 6 3 σ h 3 σ d Γ reducible 12 0 0 0 –4 0 0 0 0 0 which decomposes to T 1g + T 2g + T 1u + T 2u . In order to get the reducible representation characters, I used drawings like the following for determining the 3C 2 character: 2. Diamagnetic complexes of cobalt (III) like [Co(NH 3 ) 6 ] 3+ and [Co(en) 3 ] 3+ are orange- yellow, while paramagnetic cobalt (III) complexes like [CoF 6 ] 3– and [Co(H 2 O) 3 F 3 ] are blue. Explain, using abridged MO diagrams, this difference in color. All these complexes are octahedral. The orange-yellow complexes appear that color because they absorb (maximally) in the purple-violet region of the EM spectrum, whereas the blue complexes absorb in the orange. This means that orange-yellow complexes have a higher Δ O than the blue complexes, which makes sense because the diamagnetic complexes the energy separation between the t 2g and e g * orbitals is great enough that the electrons will overcome repulsion and pair in the t 2g orbitals before they populate the e g * level. See diagram below.
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3. Predict which complex in each of the following pairs will have the lower energy d–d transition, and give a short reason for your choice: a. [Co(NH 3 ) 5 Cl] 2+ or [Co(NH 3 ) 5
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This note was uploaded on 01/19/2012 for the course CHEM 312 taught by Professor Staff during the Summer '08 term at University of Washington.

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problem set 5 key - Chemistry 312 Problem Set 5 (due...

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