13C NMR Signal Enhancement Using Parahydrogen-Induced Polarization Mediated by a Cobalt Hydrogenation Catalyst

The use of a cobalt-based catalyst for the generation of hyperpolarized C-13 NMR resonances by parahydrogenation of ethyl acrylate is presented herein. Comparisons of the carboxylate C-13 NMR signal enhancement factor of ethyl propionate between using ((CCC)-C-mes)Co-py and a commonly utilized cationic diphosphine rhodium complex demonstrates that the cobalt system is a viable PHIP catalyst alternative. Furthermore, the operative hydrogenation mechanism of the cobalt system was examined by using H-1, C-13, and parahydrogen-induced polarization NMR spectroscopies to elucidate reaction intermediates affiliated with the observed H-1 and C-13 NMR signal enhancements in ethyl propionate.