USING 2-DIMENSIONAL NMR TECHNIQUES TO ASSIGN PROTON AND CARBON SPECTRA FOR COBALT(III) COMPLEXES DERIVED FROM LINEAR QUINQUEDENTATE LIGANDSCONTAINING NITROGEN AND SULFUR DONOR ATOMS

High resolution NMR spectroscopy was used to study the structure of a cobalt(III) complex derived from the linear quinquedentate ligand, 7-m ethyl-4,10-dithia-1,7,13-triazatridecane, NH2-CH2CH2-S-CH2CH2-N(CH3)-C H2CH2-S-CH2CH2-NH2. The flexibility of this ligand allows it theoretic ally to form four distinct structural isomers with metal ions. The one dimensional proton spectrum exhibited by [Co(NSNSN)Cl]Cl-2, is compli cated and does not provide structural insight. A combined utilization of proton, carbon, DEFT, COSY, NOESY and HETCOR spectra was employed t o establish geometric structure type, make individual proton assignmen ts, identify proton-proton connectivities that result from scalar coup ling, and distinguish interactions occurring as a result of through-sp ace interactions. Information about the five-membered chelate ring ori entations was also obtained. Two groups of signals were shown to corre late with each carbon signal, exhibiting a definite nonequivalence bet ween geminal protons. Geminal protons were found to have coupling cons tants of 14 Hz. In contrast, the vicinal protons were found to have co upling constants of 5-7 Hz.