4 research outputs found
Real-Time Detection of Intermediates in Rhodium Catalyzed Hydrogenation of Alkynes and Alkenes by Dissolution DNP
The
hydrogenation of alkynes and alkenes using Shrock–Osborn
catalysts was followed in situ with dissolution dynamic nuclear polarization
(dDNP) NMR. Natural abundance and 13C-labeled dimethyl
acetylenedicarboxylate was hyperpolarized prior to hydrogenation using
(1,4-bis{diphenylphosphino}butane)(2,5-norbornadiene) rhodium(I) perchlorate,
[Rh(NBD)(DPPB)]ClO4. The increased signal-to-noise ratio
of dDNP compared to conventional 13C NMR allowed real-time
detection of substrates and products as well as the modeling of the
hydrogenation kinetics. The build-up of an intermediate was observed
during interruption in hydrogen flow, substantiating the current view
of the reaction mechanism. Selective inversion of the carbonyl NMR
signal of the substrate was applied to demonstrate unequivocally that
the new peak appearing in the spectrum originates from a reaction
intermediate. The scope of the dDNP method for following reaction
dynamics in real time was further demonstrated by substrate competition
experiments