2-Hy-droxy-ethyl-ammonium iodide.

In the crystal structure of the title salt, C2H8NO(+)·I(-), N-H⋯O, N-H⋯I and O-H⋯I hydrogen bonds lead to the formation of layers staggered along the c axis.

Molecular vibration spectroscopy studies on novel trinuclear rhodium-7-hydride complexes of the general type {[Rh(PP*)X]3(µ(2-X)3(µ3-X)}(BF4)2 (X = H, D).

Novel trinuclear rhodium-hydride complexes with diphosphine ligands Tangphos, t-Bu-BisP*, and Me-DuPHOS which contain bridging µ(2)- and µ(3)-hydrides as well as terminal hydrides in one molecule have been reported recently. In this work, these different rhodium-hydride bonds are characterized by Raman spectroscopy and the results are compared with those obtained by means of the more commonly applied IR spectroscopy. Density functional theory (DFT) calculations have been carried out to support the experimental findings. The structure of the Rh(3)H(7) core is described in the context of their vibrational stretching modes.

Life Cycle Assessment for the Organocatalytic Synthesis of Glycerol Carbonate Methacrylate.

Bifunctional ammonium and phosphonium salts have been identified as potential organocatalysts for the synthesis of glycerol carbonate methacrylate (GCMA). Three of these catalysts showed high efficiency and allowed the conversion of glycidyl methacrylate with CO2 to the desired product in >99 % conversion and selectivity. Subsequently, immobilized analogues of selected catalysts were prepared and tested. A phenol-substituted phosphonium salt on a silica support proved to be a promising candidate in recycling experiments. The same catalyst was used in 12 consecutive runs, resulting in GCMA yields of up to 88 %. Furthermore, a life cycle assessment was conducted for the synthesis of GCMA starting from epichlorohydrin (EPH) and methacrylic acid (MAA). For the functional unit of 1 kg GCMA, 15 wt % was attributed to the incorporation of CO2 , which led to a reduction of the global warming potential of 3 % for the overall process.

Recyclable Bifunctional Polystyrene and Silica Gel-Supported Organocatalyst for the Coupling of CO2 with Epoxides.

A bifunctional ammonium salt covalently bound to a polystyrene or silica support proved to be an efficient and recyclable catalyst for the solvent-free synthesis of cyclic carbonates from epoxides and CO2 . The catalyst can be easily recovered by simple filtration after the reaction and reused in up to 13 consecutive runs with retention of high activity and selectivity even at 90 °C. The scope and limitations of the reaction has been evaluated in terms of reaction conditions and substrate scope.

Highly Efficient Polymer-Supported Catalytic System for the Valorization of Carbon Dioxide.

Polydibenzo-18-crown-6 was utilized as a co-catalyst and polymeric support in combination with potassium iodide for the synthesis of cyclic carbonates from carbon dioxide and epoxides under mild and solvent-free conditions. The efficiency of this catalytic system can be easily increased by loading the polymer with KI prior to the reaction. The influence of various reaction parameters were studied thoroughly. The scope and limitation of the catalyst system was studied at 80 °C and 100 °C. A large number of terminal epoxides (14) were converted to the desired cyclic carbonates in yields up to 99%. We could successfully recover and reuse the catalyst >20 times with excellent yields up to 99%. Although, we observed that the activity gradually decreased after repetitive cycles. This decrease was attributed to KI leaching and partial degradation caused by mechanical stirring. This assumption is supported by scanning electron microscopy and energy dispersive X-ray spectroscopy.

Direct experimental and computational evidence for the dihydride pathway in TangPHOS-Rh catalysed asymmetric hydrogenation.

DFT computations of various possible reaction pathways in asymmetric hydrogenation of methyl (Z-α)acetylaminocinnamate catalysed by Rh-TangPHOS complex revealed the clear preference of the dihydride pathway. This conclusion was explicitly confirmed by the structure of the monohydride intermediate intercepted in the low temperature NMR hydrogenation experiments. DFT analysis of the origin of enantioselection showed that it takes place via obstructing the proper coordination of the double bond in the S-enantioselective pathway.

Trinuclear rhodium hydride complexes.

Three novel trinuclear rhodium hydride complexes of the type {[Rh(PP*)H](3)(µ(2)-H)(3)(µ(3)-H)}[BF(4)](2) containing diphosphines Tangphos, t-Bu-BisP* and Me-DuPHOS have been synthesised. The new compounds are very stable. Their structures have been characterized by X-ray analysis in the solid state and by NMR-spectroscopic investigations in solution.