2D NMR EXCHANGE SPECTROSCOPY WITH SPY NUCLEI FOR THALLIUM(III) CYANOCOMPLEXES IN AQUEOUS-SOLUTION

We have used a combination of C-13 and Tl-205 NMR 2D exchange spectroscopy (EXSY) to study cyanide exchange reactions in an aqueous solution containing the recently established complexes (Tl(CN)3)-C-13 and (Tl(CN)4-)-C-13, and (HCN)-C-13. Because of the well-resolved heteronuclear spin-spin couplings (up to 8 kHz), the system was considered to have six exchanging sites for C-13 NMR and nine for Tl-205 NMR. The employed method gave an overview of the dynamic processes at chemical equilibrium. It is shown that in such systems otherwise invisible kinetic information can be brought into light. The EXSY spectra were evaluated quantitatively for both nuclei, and rate constants were calculated for the different exchange pathways.