Modifications to the Experiment for the Synthesis of [(Λ or
Δ)-Co(diNOsar)]Br3
The following four steps were added to more fully evaluate the
structure of the [Co(diNOsar)]Br3 product (synthesized as
outlined in Scheme II).
1. Two-dimensional NMR techniques (COSY, HMQC or
HETCOR, and NOESY) are used to examine the
structure of the (Λ or Δ)-Co(diNOsar)Br3 product
(Scheme II) and its partially deuterated analogs.
2. The 1
H NMR spectrum of Λ-Co(en)3I3 is compared to
that of Λ-Co(diNOsar)Br3 to highlight the contrasting
structural implications.
3. Three-dimensional visualizations were created to help
students assign the chemically equivalent protons and
magnetically inequivalent protons in the product.
4. Circular dichroism (CD) spectroscopy is then used to
examine the enantiomeric excesses of the products and to
further explore the features (not observed) in the optical
spectroscopy. A discussion of the published literature on
the CD spectroscopy of Λ-Co(en)3
3+ (single crystal and
solution) and Λ-Co(diNOsar)3+ is illuminating.