A modular family of phosphine-phosphoramidite ligands and their hydroformylation catalysts : steric tuning impacts upon the coordination geometry of trigonal bipyramidal complexes of type [Rh(H)(CO)2(P^P*)]

The authors thank the Eastman Chemical Company for funding.Four new phosphine-phosphoramidite bidentate ligands have been synthesised and studied in rhodium-catalysed hydroformylation. Variable temperature NMR studies have been used along with HPIR to investigate the coordination mode of the trigonal bipyramidal complexes formed from [Rh(acac)(CO)2], ligand and syngas. It was found that small changes to the ligand structure have a large effect on the geometry of the active catalytic species. The rhodium catalysts of these new ligands were found to give unusually high iso-selectivity in the hydroformylation of propene and 1-octene.PostprintPeer reviewe

Composition of catalyst resting states of hydroformylation catalysts derived from bulky mono-phosphorus ligands, rhodium dicarbonyl acetylacetonate and syngas

We thank the Eastman Chemical Company for funding of RCH, EPSRC for funding of PD (EP003868/1).The paper describes the composition of the resting states of several catalysts for alkene hydroformylation derived from bulky monophosphorus ligands. The results presented assess how bulky ligands compete with CO for the rhodium, and hence the role of ‘unmodified’ catalysts in alkene hydroformylation in the presence of these ligands. High Pressure Infra-Red (HPIR) spectroscopy was carried out at the rhodium and syngas concentrations typically used during catalysis experiments. These HPIR studies revealed that two ligands previously studied in Rh-catalysed hydroformylation react with [Rh(acac)(CO)2] and H2/CO to give the unmodified rhodium cluster, [Rh6(CO)16], as the only detectable species. Both less bulky phosphoramidites, and 1,3,5,7-Tetramethyl-6-phenyl-2,4,8-trioxa-6-phosphaadamantane, on the other hand, do not show the presence of [Rh6(CO)16], and hence catalysis proceeds by purely ligand modified species under normal conditions. In the case of the Rh/ phosphaadamantane catalysts, anecdotal evidence that this only forms a particularly useful catalyst above a certain pressure threshold can be understood in terms of how the catalyst composition varies with pressure. The ligands discussed have all been assessed in the hydroformylation of propene to separate their innate branched selectivity from their ability to isomerise higher alkenes to internal isomers.PostprintPeer reviewe

Liquid–Liquid Equilibria of Ionic Liquids–Water–Acetic Acid Mixtures

International audienceThe liquid–liquid equilibria of ionic liquid-based systems with water and/or acetic acid have been studied at 293.15 K and atmospheric pressure. One hydrophilic ionic liquid and a series of hydrophobic ionic liquids were investigated in order to examine their effect on the separation of water and acetic acid mixtures. The ionic liquids studied were [P666,14]Cl, [P666,14][NTf2], [C4mmim][NTf2], [Cnmim][NTf2] (n = 2, 4, 6, 8, or 10), [C4mpyrr][NTf2], [N1114][NTf2], and [C2mim][EtSO4]. [C2mim][EtSO4] is totally miscible with water and acetic acid in all compositions. Comparing [P666,14]Cl with [P666,14][NTf2], the former showed higher extraction selectivities; however, due to the larger viscosity of [P666,14]Cl, the [NTf2]− based ionic liquids offer a better solvent choice for the liquid extraction processes. As expected, as the solubility of water decreases with increasing the chain length of ionic liquids, this in turn leads to [C10mim][NTf2] showing greater acetic efficiency than [C2mim][NTf2] for the separation of water and acetic acid. The experimental data obtained for ternary systems containing the [C4mmim][NTf2] demonstrated that the modification of the C(2) position on the imidazolium ring does not significantly affect the selectivity compared with [C4mim][NTf2]. Tetraalkyl ammonium and N-alkyl pyrrolidinium based ionic liquids were also studied with the [NTf2]− anion with the results for the system containing the [C4mpyrr][NTf2] demonstrating a higher selectivity for the separation of water and acetic acid than the other [NTf2]− based systems studied. All experimental data were then correlated using the UNIQUAC model within an accuracy close to 1.6%. Finally, the ionic liquids were also compared with standard molecular extraction solvent, for example, methyl tert-butyl ether and methyl isobutyl ketone. The organic solvents showed an advantage over the [Cnmim][NTf2]-based ionic liquids but only over a narrow composition range. In all ionic liquid systems, the selectivity remains high at low acetic acid concentration compared with that found in the organic solvents, which is important for practical operation and demonstrates the advantages of using an ionic liquid for the extraction

Abstracts from the 8th International Conference on cGMP Generators, Effectors and Therapeutic Implications

This work was supported by a restricted research grant of Bayer AG

Transition-Metal-Catalyzed Regeneration of Nicotinamide Coenzymes with Hydrogen\u3csup\u3e1\u3c/sup\u3e

The nicotinamide coenzymes consumed in alcohol dehydrogenase catalyzed enantioselective reduction of ketones are expensive and thus require recycling. We have demonstrated that ruthenium(II) and rhodium(III) complexes are effective catalysts for the reduction of nicotinamide coenzymes with hydrogen, under conditions that are appropriate for in situ coupling with enzymatic reductions. The nicotinamide coenzymes consumed in alcohol dehydrogenase catalyzed enantioselective reduction of ketones are expensive and thus require recycling. We have demonstrated that ruthenium(II) and rhodium(III) complexes are effective catalysts for the reduction of nicotinamide coenzymes with hydrogen, under conditions that are appropriate for in situ coupling with enzymatic reductions

Process for Stabilizing Enzymes with Phosphine or Phosphite Compounds

The invention relates to processes for stabilizing the activity of an enzyme, comprising mixing a phosphine or phosphite with an oxidoreductase enzyme

Transition-Metal-Catalyzed Regeneration of Nicotinamide Coenzymes with Hydrogen\u3csup\u3e1\u3c/sup\u3e

The nicotinamide coenzymes consumed in alcohol dehydrogenase catalyzed enantioselective reduction of ketones are expensive and thus require recycling. We have demonstrated that ruthenium(II) and rhodium(III) complexes are effective catalysts for the reduction of nicotinamide coenzymes with hydrogen, under conditions that are appropriate for in situ coupling with enzymatic reductions. The nicotinamide coenzymes consumed in alcohol dehydrogenase catalyzed enantioselective reduction of ketones are expensive and thus require recycling. We have demonstrated that ruthenium(II) and rhodium(III) complexes are effective catalysts for the reduction of nicotinamide coenzymes with hydrogen, under conditions that are appropriate for in situ coupling with enzymatic reductions