A set of novel phosphine-phosphoramidite ligands possessing two elements of chirality have been prepared through a modular synthetic approach.

A continuous-flow process for the asymmetric hydrogenation of methyl propionylacetate as a prototypical b-keto ester in a biphasic system of ionic liquid and supercritical carbon dioxide (scCO 2 ) is presented. An established ruthenium/2,2'-bis(diphenylphosphino)-1,1'-binaphthyl (BINAP) catalyst was immobilised in an imidazolium-based ionic liquid while scCO 2 was used as mobile phase transporting reactants in and products out of the reactor. The use of acidic additives led to significantly higher reaction rates and enhanced catalyst stability albeit at slightly reduced enantioselectivity. High single pass conversions (> 90%) and good enantioselectivity (80-82% ee) were achieved in the first 80 h. The initial catalyst activity was retained to 91% after 100 h and to 69% after 150 h time-on-stream, where-as the enantioselectivity remained practically constant during the entire process. A total turnover number of~21,000 and an averaged space-time yield (STY av ) of 149 g L À1 h À1 were reached in a long-term experiment. No ruthenium and phosphorus contaminants could be detected via inductively coupled plasma optical emission spectrometry (ICP-OES) in the product stream and almost quantitative retention by the analysis of the stationary phase was confirmed. A comparison between batch-wise and continuous-flow operation on the basis of these data is provided.

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We performed electronic structure calculations within density functional theory including ab initio molecular dynamic simulations of isolated Fe 13 and Fe 55 clusters. We observed the energy preference of icosahedral over cuboctahedral clusters for both Fe 13 and Fe 55 . The magnetic structure is ferromagnetic for Fe 13 clusters, but anti-ferromagnetic for Fe 55 clusters. The isolated clusters exhibit a HOMO-LUMO gap. Subsequently, we modeled the embedding of Fe 13 and Fe 55 clusters in silica glass, creating several models of different size. All models show a homogeneous trend after optimization, however. For embedded clusters we observed the formation of an iron oxide interface between the cluster and the dielectric matrix. The magnetization of the embedded clusters is slightly larger than the magnetization of free clusters. The small clusters retain their electronic structure around the Fermi-level, still exhibiting a HOMO-LUMO gap, despite some major geometrical distortions of the clusters.Mater. Res. Soc. Symp. Proc. Vol. 959

Enantioselective syntheses O 0031Highly Efficient and Versatile Phosphine-Phosphoramidite Ligands for Asymmetric Hydrogenation. -The novel ligands possessing two elements of chirality are found to be unique in providing excellent enantioselectivities for hydrogenations of C=C, C=O, and C=N double bonds in combination with three different transitions metals (rhodium, ruthenium, and iridium). -(EGGENSTEIN, M.; THOMAS, A.; THEUERKAUF, J.; FRANCIO*, G.; LEITNER, W.; Adv. Synth. Catal. 351 (2009) 5, 725-732; Inst. Tech. Makromol. Chem.,