Hydroformylation of olefins with the water soluble HRh(CO)[P(m-C6H4SO3Na)3]3 in supported aqueous-phase. Is it really aqueous?

Unlocking the potential of supported liquid phase catalysts with supercritical fluids: low temperature continuous flow catalysis with integrated product separation

Solution-phase catalysis using molecular transition metal complexes is an extremely powerful tool for chemical synthesis and a key technology for sustainable manufacturing. However, as the reaction complexity and thermal sensitivity of the catalytic system increase, engineering challenges associated with product separation and catalyst recovery can override the value of the product. This persistent downstream issue often renders industrial exploitation of homogeneous catalysis uneconomical despite impressive batch performance of the catalyst. In this regard, continuous-flow systems that allow steady-state homogeneous turnover in a stationary liquid phase while at the same time effecting integrated product separation at mild process temperatures represent a particularly attractive scenario. While continuous-flow processing is a standard procedure for large volume manufacturing, capitalizing on its potential in the realm of the molecular complexity of organic synthesis is still an emerging area that requires innovative solutions. Here we highlight some recent developments which have succeeded in realizing such systems by the combination of near- and supercritical fluids with homogeneous catalysts in supported liquid phases. The cases discussed exemplify how all three levels of continuous-flow homogeneous catalysis (catalyst system, separation strategy, process scheme) must be matched to locate viable process conditions.

Nonionic Tenside Ligands and its Application in Biphasic Catalysis

This review article mainly surveys our research results of biphasic catalysis with nonionic tenside ligands. Emphasis is given to the synthesis and property of cloud point of the nonionic tenside ligands, the general principles of thermoregulated phase-transfer catalysis (TRPTC) and thermoregulated phase-separable catalysis (TPSC). It also explores the applications of TRPTC and TPSC in the hydroformylation of higher olefins and CO selective reduction of nitroarenes. The introduction of TRPTC to biphasic systemis free from the shortcomings of classical aqueous/organic two-phase catalysis, in which the application scope is restrained by the water solubility of the organic substrate. The biphasic catalysis with nonionic tenside ligands was characterized by homogeneous catalysis coupled with convenient biphasic separation.

Importance of Interfacial Adsorption in the Biphasic Hydroformylation of Higher Olefins Promoted by Cyclodextrins: A Molecular Dynamics Study at the Decene/Water Interface

We report herein a molecular dynamics study of the main species involved in the hydroformylation of higher olefins promoted by cyclodextrins in 1-decene/water biphasic systems at a temperature of 350 K. The two liquids form a well-defined sharp interface of approximately 7 A width in the absence of solute; the decene molecules are generally oriented "parallel" to the interface where they display transient contacts with water. We first focused on rhodium complexes bearing water-soluble TPPTS(3-) ligands (where TPPTS(3-) represents tris(m-sulfonatophenyl)phosphine) involved in the early steps of the reaction. The most important finding concerned the surface activity of the "active" form of the catalyst [RhH(CO)(TPPTS)(2)](6-), the [RhH(CO)(2)(TPPTS)(2)](6-) complex, and the key reaction intermediate [RhH(CO)(TPPTS)(2)(decene)](6-) (with the olefin pi-coordinated to the metal center) which are adsorbed at the water side of the interface in spite of their -6 charge. The free TPPTS(3-) ligands themselves are also surface-active, whereas the -9 charged catalyst precursor [RhH(CO)(TPPTS)(3)](9-) prefers to be solubilized in water. The role of cyclodextrins was then investigated by performing simulations on 2,6-dimethyl-beta-cyclodextrin ("CD") and its inclusion complexes with the reactant (1-decene), a reaction product (undecanal), and the corresponding key reaction intermediate [RhH(CO)(TPPTS)(2)(decene)](6-) as guests; they were all shown to be surface-active and prefer the interface over the bulk aqueous phase. These results suggest that the biphasic hydroformylation of higher olefins takes place "right" at the interface and that the CDs promote the "meeting" of the olefin and the catalyst in this peculiar region of the solution by forming inclusion complexes "preorganized" for the reaction. Our results thus point to the importance of adsorption at the liquid/liquid interface in this important phase-transfer-catalyzed reaction.

Multiphasic heterogeneous catalysis mediated by catalyst-philic liquid phases

This critical review addresses heterogeneous catalysis in systems where multiple liquid phases coexist and where one of the phases is catalyst-philic. This technique provides built-in catalyst separation, and product recovery for organic reactions. Focus is placed on the components of the multiphasic systems with emphasis on the constituents of the catalyst-philic phases (PEGs, onium salts, ionic liquids) that incorporate the catalysts, as well as on the effects on catalytic efficiency. It collects a wide body of scattered information that is often labelled with different terms.