Additional Analyses of the Λ and Δ-Co(en)3
3+ Structures
Before continuing to the synthesis of the Sargeson encapsulated
product, students carry out standard characterization techniques
on their Co(en)3
3+ products; determining the %ee by
measuring optical rotation and analyzing the molecular
structure by taking 1
H NMR and 13C NMR spectra. Students
also set aside a small portion (10−20 mg) of their product for
later spectroscopic analysis performed simultaneously with the
analysis of Co(diNOsar)Br3. At this point in the experiment, we
pause to discuss symmetry and chirality in metal complexes, the
assignment of the absolute configuration of the stereochemistry
around the metal center, and the possible conformers created
by the λ and δ ligand twists within the complex. The four
conformers of the Λ form of Co(en)3
3+ are shown in Figure 1.
Three-dimensional interactive visualizations written with
JSmol6 commands are available to facilitate teaching the
assignment of Λ and Δ absolute configurations and λ and δ
ligand twists (see “The Structure and Symmetry of the Metal
Tris Chelates”
7
) and visualizations created specifically for this
experiment show the Λ and Δ forms of Co(en)3
3+, Λ and Δ
forms of Co(diNOsar)3+, and the four conformers of Λ-
Co(en)3
3+ (see “Visualizations for the Advanced Inorganic
Chemistry Laboratory at Carleton College”).8
Additional Analyses of the Λ and Δ-Co(en)33+ StructuresBefore continuing to the synthesis of the Sargeson encapsulatedproduct, students carry out standard characterization techniqueson their Co(en)33+ products; determining the %ee bymeasuring optical rotation and analyzing the molecularstructure by taking 1H NMR and 13C NMR spectra. Studentsalso set aside a small portion (10−20 mg) of their product forlater spectroscopic analysis performed simultaneously with theanalysis of Co(diNOsar)Br3. At this point in the experiment, wepause to discuss symmetry and chirality in metal complexes, theassignment of the absolute configuration of the stereochemistryaround the metal center, and the possible conformers createdby the λ and δ ligand twists within the complex. The fourconformers of the Λ form of Co(en)33+ are shown in Figure 1.Three-dimensional interactive visualizations written withJSmol6 commands are available to facilitate teaching theassignment of Λ and Δ absolute configurations and λ and δligand twists (see “The Structure and Symmetry of the MetalTris Chelates”7) and visualizations created specifically for thisexperiment show the Λ and Δ forms of Co(en)33+, Λ and Δforms of Co(diNOsar)3+, and the four conformers of Λ-Co(en)33+ (see “Visualizations for the Advanced InorganicChemistry Laboratory at Carleton College”).8
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