Insight into catalyst speciation and hydrogen co-evolution during enantioselective formic acid-driven transfer hydrogenation with bifunctional ruthenium complexes from multi-technique operando reaction monitoring

Abstract

Operando spectroscopy shows a transition from dehydrogenation to hydrogen transfer during the reaction, and allows measuring optimal conditions for maximum rate and efficiency.

Multi-nuclear, high-pressure, operando FlowNMR spectroscopic study of Rh/PPh3 – catalysed hydroformylation of 1-hexene

“…When 10 -20 equivalents of PPh 3 were added high chemo-and regio-selectivities were maintained, but at reduced overall reaction rates due to PPh 3 competing with the olefin substrates for coordination to the Rh centre. Again, this behaviour is well documented in the literature, 40 and the overall rates observed in our FlowNMR studies (Table S4) As in some of our previous work, 41 it was also possible to track the amount of H 2 dissolved in solution by 1 H FlowNMR during the hydroformylation reaction ( Figure 8) after considering flow effects and the ortho/para ratio of H 2 at 50 °C. 42 Ensuring that the volume element cycle.…”

Operandomonitoring of mechanisms and deactivation of molecular catalysts

“…1. 159,162 Reproduced and adapted with permission from the American Chemical Society. 163 (24) are formed first and afterwards, after hydrogenation of norbornadiene, the cyclooctadiene complexes ( 25) emerge (Fig.…”

“…While this shows the power of a flow NMR setup in combination with signal enhancement techniques for operando studies, a consecutive work by the same group can be used as a practical example of the use of multiple complementing techniques. 162 The authors investigated the same reaction but using formic acid as H-donor instead of isopropanol. The flow NMR setup from the previous study was expanded by a HPLC, a UVvis spectrometer and a gas phase mass-spectrometer installed on the reactor.…”

Does the Configuration at the Metal Matter in Noyori–Ikariya Type Asymmetric Transfer Hydrogenation Catalysts?

“…We have previously reported how online FlowNMR spectroscopy may be used to study the speciation and kinetics of Noyori’s catalyst during ketone transfer hydrogenation from isopropanol 12 and from formic acid/triethylamine mixtures. 11 …”