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

Abstract

Homogeneous ruthenium complexes modified by imidazole-substituted monophosphines as catalysts for various highly efficient hydroformylation reactions were characterized by in situ IR spectroscopy under reaction conditions and NMR spectroscopy. A proper protocol for the preformation reaction from [Ru3 (CO)12] is decisive to prevent the formation of inactive ligand-modified polynuclear complexes. During catalysis, ligand-modified mononuclear ruthenium(0) carbonyls were detected as resting states. Changes in the ligand structure have a crucial impact on the coordination behavior of the ligand and consequently on the catalytic performance. The substitution of CO by a nitrogen atom of the imidazolyl moiety in the ligand is not a general feature, but it takes place when structural prerequisites of the ligand are fulfilled.

From Internal Olefins to Linear Amines: Ruthenium-Catalyzed Domino Water–Gas Shift/Hydroaminomethylation Sequence

“…Changing the imidazolyl moiety to pyrrol, pyrazol, and aromatic type ligands (L 8 –L 10 ), the catalytic performance declined. These results demonstrate that a hemilabile behavior between the imine nitrogen of the imidazolyl unit and the ruthenium center may play an important role in this catalytic transformation…”

Carbon Dioxide Transformation in Imidazolium Salts: Hydroaminomethylation Catalyzed by Ru‐Complexes

“…Therefore, the reported catalytic system is one of the most active to allow the use of CO 2 as aC Os ource as for example in hydroformylation of alkenes. [33] In theseh ydroformylation reactions, preliminarys pectroscopic( IR and NMR) investigations have revealed the involvemento fR u-hydride-carbonyl-carbene complexesa sp ossible catalytic active species [33] akin to observed in the hydroformylation using CO. [49] 1 Ha nd 13 CH PNMR experiments have been performed to investigate the naturea nd structure of the species formed by dissolving Ru 3 (CO) 12 either in the 1-n-butyl-3-methyl-imidazolium chloride ([BMI]Cl) or 1-nbutyl-2,3-dimethyl-imidazolium chloride ([BMMI]Cl). The main resultsa re summarized in Scheme 5a nd ad etailed discussion Figure SI1-SI6).…”

Highly active and stable porous polymer heterogenous catalysts for decomposition of formic acid to produce H2

“…1d). The results reveal that the two absorption peaks of Ru@POPs-PPh3 at 2057 and 1996 cm -1 can be attributed to CO bound to Ru (II), while Ru@POPs-TPP shows peaks at 2066 and 2015 cm -1 [30]. The difference in wavenumbers between Ru@POPs-TPP and Ru@POPs-PPh3 indicates that the different types of ligands in the polymer framework affect the energy state of CO bound to Ru; this is assumed to be closely related to the electron density of Ru, and further affects the performance of the catalysts during the decomposition of FA.…”