Investigation into the Equilibrium of Iridium Catalysts for the Hydroformylation of Olefins by Combining In Situ High-Pressure FTIR and NMR Spectroscopy

Abstract

A detailed quantitative study of phosphine-modified hydrido iridium complexes relevant for the hydroformylation reaction has been performed using HP-FTIR and HP-NMR spectroscopy. The equilibrium composition under typical reaction conditions has been characterized. Investigation of the temperature dependency allowed even for a distinction between both configurational isomers of [HIr(CO)2(PPh3)2]. The trihydride complex [H3Ir(CO)(PPh3)2] is part of the investigated equilibrium depending on the ratio of p(H2)/p(CO). Single rate constants for the sequence of corresponding equilibrium reactions have been estimated from stopped-flow experiments and conventional measurements, monitoring the concentrations after changing reactant concentrations.

In Situ FTIR and NMR Spectroscopic Investigations on Ruthenium‐Based Catalysts for Alkene Hydroformylation

“…The reaction of [Ru 3 (CO) 12 ]w ith L1, L2,a nd L3 under argon at 100 8Cf or 60 min led mostp robablyt ot he same type of phosphido-bridged complexes, because we observed signals at d …”

“…For the IR spectroscopics tudy we chose the hydroformylation of 3,3-dimethyl-1-butene with [Ru 3 (CO) 12 ]/L (Scheme 2). Experimentsw ere performed at 100 8C, p(CO) = 2.…”

“…The experiments with Ru/L5 and Ru/L6 gave ap lausible rationalization for the observed poor catalytic performance. In the IR spectra, [Ru(CO) 5 ]a nd [Ru 3 (CO) 12 ]w ere observed as the dominant detectable rutheniums pecies (Figure 10). In the 31 PNMR spectra of the reaction solutions only the signals of the free ligands at d( 31 P) = 5.5 ppm (Ru/L5)a nd d( 31 P) = 5.6 ppm (Ru/L6) were found.…”

“…[40] The micro gear pump was set to 2333 rpm (displacement volume: 48 mL). 12 ]a tr oom temperature, the solutions were heated and handled at 50 8C. Preformation routine 1: the solution was heated to 100 8Cp rior to the addition of the gases.…”

“…The full sets of IR spectra collected for the systems including [Ru 3 (CO) 12 ]/L (L = L2, L3)a re giveni nt he Supporting Information SI-C. 1 H, 15 NHMBCN MR spectra (benzene solution) of the free ligand L3 (red) andthe Ru/L3 carbonyl complexo btained after preformationw ithout syngas (black). Figure 6s hows the X-ray molecular structure.…”