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Plessow P.,BASF | Plessow P.,CaRLa Catalysis Research Laboratory
Journal of Chemical Theory and Computation

This letter describes a chain-of-states method that optimizes reaction paths under the sole constraint of equally spaced structures. In contrast to NEB and string methods, it requires no spring forces, interpolation algorithms, or other heuristics to control structure distribution. Rigorous use of a quadratic PES allows calculation of an optimization step with a predefined distribution in Cartesian space. The method is a formal extension of single-structure quasi-Newton methods. An initial guess can be evolved, as in the growing string method. © 2013 American Chemical Society. Source

Limbach M.,CaRLa Catalysis Research Laboratory | Limbach M.,BASF
Advances in Organometallic Chemistry

For more than three decades, the catalytic synthesis of acrylates from the cheap and abundantly available C1 building block CO2 and alkenes has been an unsolved problem in catalysis research, both in academia and industry. Acrylates and their downstream products are ubiquitous in daily life as hygiene products, coatings, adhesives, or plastics, etc., and they are manufactured globally on a multimillion ton level. Thus, a CO2-based route to such world-scale chemicals is economically most attractive, but, due to thermodynamic and kinetic hurdles, also highly challenging. Since the revolutionary work of Hoberg et al., metallalactones are discussed as possible intermediates in a catalytic cycle, but the reaction has not been existing until recently.Herein, we present our and others' efforts on the development of a homogeneous catalyst that permits the catalytic synthesis of salts of α,β-unsaturated acids from CO2, alkenes, and a base. As this turned out to be difficult without a deeper mechanistic understanding, we highlight most recent mechanistic findings and also elaborate on unproductive reaction pathways. © 2015 Elsevier Inc. Source

Cao P.,CaRLa Catalysis Research Laboratory | Cabrera J.,CaRLa Catalysis Research Laboratory | Padilla R.,CaRLa Catalysis Research Laboratory | Serra D.,CaRLa Catalysis Research Laboratory | And 3 more authors.

Cationic platinum(II) complexes with bi- or tridentate (pincer) functionalized NHC ligands were found to be catalytically active in the hydroamination of unactivated alkenes. In some cases, the presence of water had an activating effect on the complexes. Reactions with the N-nucleophilic substrate morpholine led to a noncatalytic reaction in which the deprotonation product of the key cationic β-aminoalkyl platinum complex could be isolated and characterized. Surprisingly, attempted protonation of this complex did not give the expected N-alkylated product, indicating either the thermodynamic unfavorability of C-Pt bond cleavage or its kinetic inertness. © 2012 American Chemical Society. Source

Schachner J.A.,CaRLa Catalysis Research Laboratory | Cabrera J.,CaRLa Catalysis Research Laboratory | Padilla R.,CaRLa Catalysis Research Laboratory | Fischer C.,BASF | And 5 more authors.
ACS Catalysis

We report on a series of six new pyridinealkoxide-bridged first and second generation ruthenium carbenes with similar or even higher activity in ring-opening metathesis polymerization (ROMP), cross metathesis (CM), and ring closing metathesis (RCM) reactions than state-of-the-art catalysts. The new precatalysts show an extraordinarily high stickiness to commercially available silica, which significantly enhances their adsorptive separation from unprocessed reaction mixtures. © 2011 American Chemical Society. Source

Manzano R.,CaRLa Catalysis Research Laboratory | Wurm T.,University of Heidelberg | Rominger F.,University of Heidelberg | Hashmi A.S.K.,CaRLa Catalysis Research Laboratory | And 2 more authors.
Chemistry - A European Journal

A number of saturated abnormal N-heterocyclic carbene (NHC) complexes of gold, in combination with KBArF4 as activator, were successfully applied in the chemoselective addition of hydrazine to alkynes. The reaction proceeds even at room temperature, which was not possible to date with gold catalysts. The reaction can be applied to a number of substituted arylalkynes. With alkylalkynes the yields are low. The saturated abnormal NHC ligands are resistant to isomerization to the saturated normal NHC coordination mode under basic reaction conditions. Under acidic conditions, a simple protonation at the nitrogen atom not neighboring the carbene center was observed and unambiguously characterized by an X-ray crystal-structure analysis. Computational studies confirm that such an isomerization would be highly exothermic, the observed kinetic stability probably results from the need to shift two protons in such a process. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

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