Slow Inversion of Coordinated Thioether Groups in SNS-Type Ruthenium Pincer Complexes

The thioether-group-containing SNS-type pincer complex [({EtSCH₂CH₂}₂NH)RuCl(H)(PPh₃)] ( 2 ) exists in three different diastereomers ( 2 a – c ). The molecular structures obtained from single crystal X-Ray diffraction studies of all three isomers reveal a difference in the relative orientation of the respective EtS-groups, while other commonly observed diastereomers as the result of cis-/trans- or fac-/mer-isomerism are not observed. Chemical exchange between the three diastereomers 2 a – c was discovered by phase-sensitive ¹H and ³¹P NOESY NMR spectroscopy, and further quantified by line shape analysis of ¹H NMR spectra. The experimentally derived averaged Gibbs energies of activation for the interconversion of the isomers (65–70 kJ/mol) are in good agreement with the results obtained from DFT calculations, which suggest an inversion of the ligating sulfur atoms, although a dissociative pathway for the configurational inversion can be competitive.     

Carbon Deposit Analysis in Catalyst Deactivation,Regeneration, and Rejuvenation

Hydrocarbon conversion catalysts suffer from deactivation by deposition or formation of carbon deposits. Carbon deposit formation is thermodynamically favored above 350 °C, even in some hydrogen-rich environments. We discuss four basic mechanisms: a carbenium-ion based mechanism taking place on acid sites of zeolites or bifunctional catalysts, a metal-induced formation of soft coke (i.e., oligomers of small olefins) on bifunctional catalysts, a radical-mediated mechanism in higher-temperature processes, and fast-growing carbon filament formation. Catalysts deactivate because carbon deposits block pores at different length scales, or directly block active sites. Some deactivated catalysts can be re-used, others can be regenerated or have to be discarded. Catalyst and process design can mitigate the effects of deactivation. New analytical tools allow for the direct observation (in some cases even under in situ or operando conditions) of the 3D-distribution of coke-type species as a function of catalyst structure and lifetime.     

Modeling nutrient impacts on microalgae cells via image analyses

A nonlinear multivariate regression methodology is presented for modeling the responses of microalgae cells regarding their physical appearance (size, shape) to shifts in their chemical environment. This chemometric approach builds on a novel image analysis method recently published in this Journal and augments it such that: (i) the measured effect is expressed mathematically rather than described empirically and (ii) incorporates effects of multiple ambient parameters so that their interactions can be investigated. Copyright © 2013 John Wiley & Sons, Ltd.