Homogeneous hydrogenation of norbornadiene with parahydrogen and phosphonic ester phosphine rhodium complexes studied by in situ NMR spectroscopy

Article abstract of DOI:10.1016/0040-4020(95)00687-4

Homogeneous hydrogenation of norbornadiene with enriched parahydrogen (p-H₂) and phosphonic ester phosphine rhodium complexes is detected using in situ NMR spectroscopy. The obtained polarization spectra remain unchanged during the catalysis of thf-d₈ as a solvent but change with time when the hydrogenation is executed in acetone-d₆. The observed phenomenon is attributed to a change of the phase correlation of the transferred parahydrogen nuclei via nuclear singlet-triplet (S/T₀) mixing during the reaction. Simultaneously, ³¹P NMR spectra change indicating a change in the nature of the original rhodium complex when the hydrogenation is carried out in acetone-d₆.