Bis-(thiosemicarbazonato) Zn(II) complexes as building blocks for construction of supramolecular catalysts

In this paper we report the application of bis-(thiosemicarbazonato) Zn(II) complexes as building blocks in the construction of supramolecular transition metal assemblies. We investigated their coordination behaviour towards pyridylphosphine molecules and found these systems comparable to those based on Zn ( porphyrin) and Zn(salphen) complexes. Additionally, catalytic experiments and an in situ high-pressure FTIR study of the supramolecular rhodium hydroformylation catalysts, assembled using the bis- (thiosemicarbazonato) Zn(II) complexes, demonstrate their applicability in supramolecular catalysis and their potential for application in other areas of supramolecular chemistry

Selective recovery of palladium using an innovative functional polymer containing phosphine oxide

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Capsule-controlled selectivity of a rhodium hydroformylation catalyst

Chemical processes proceed much faster and more selectively in the presence of appropriate catalysts, and as such the field of catalysis is of key importance for the chemical industry, especially in light of sustainable chemistry. Enzymes, the natural catalysts, are generally orders of magnitude more selective than synthetic catalysts and a major difference is that they take advantage of well-defined cavities around the active site to steer the selectivity of a reaction via the second coordination sphere. Here we demonstrate that such a strategy also applies for a rhodium catalyst; when used in the hydroformylation of internal alkenes, the selectivity of the product formed is steered solely by changing the cavity surrounding the metal complex. Detailed studies reveal that the origin of the capsule-controlled selectivity is the capsule reorganization energy, that is, the high energy required to accommodate the hydride migration transition state, which leads to the minor product

Selective extraction of PGM by a dynamic sorption-filtration on a phosphine oxide based polymer powder

International audienc

Capsule-controlled selectivity of a rhodium hydroformylation catalyst

Chemical processes proceed much faster and more selectively in the presence of appropriate catalysts, and as such the field of catalysis is of key importance for the chemical industry, especially in light of sustainable chemistry. Enzymes, the natural catalysts, are generally orders of magnitude more selective than synthetic catalysts and a major difference is that they take advantage of well-defined cavities around the active site to steer the selectivity of a reaction via the second coordination sphere. Here we demonstrate that such a strategy also applies for a rhodium catalyst; when used in the hydroformylation of internal alkenes, the selectivity of the product formed is steered solely by changing the cavity surrounding the metal complex. Detailed studies reveal that the origin of the capsule-controlled selectivity is the capsule reorganization energy, that is, the high energy required to accommodate the hydride migration transition state, which leads to the minor product

Selective recovery of palladium by a process coupling sorption on a functional polymer containing phosphine oxide and filtration

International audienceLes métaux du groupe platine (ou PGM pour Platinum Group Metals) sont utilisés dans denombreux domaines notamment pour leurs propriétés catalytiques. Bien que le recyclage deces métaux soit en plein essor, la principale source d’approvisionnement provient del’exploitation des mines de cuivre et de nickel qui peuvent contenir jusqu’à 10 g de PGM partonne de minerais. Les méthodes d’extraction actuelles consistent à concentrer les métaux parflottation et incinération, puis à les séparer via des procédés hydrométallurgiques aprèsdissolution dans des solutions acides (HCl). Les PGM étant souvent à l’état de trace dans cesmatrices, le développement de nouvelles méthodes permettant leur extraction sélective et leurconcentration revêt une importance capitale.Cette étude s’intéresse à l’extraction du Pd à partir d’effluents synthétiques de type miniers parsorption sélective sur un polymère fonctionnel innovant en poudre à base de groupementsoxydes d’aminophosphine (MP-102, Magpie-Polymers), tant d’un point de mécanistique quemise en oeuvre au sein d’un procédé de traitement pseudo-continu.Il a été montré qu’à partir d’une solution contenant du Pd, Cu et Ni, le MP-102 sorbaitpréférentiellement le Pd notamment à pH acide (96% à pH 1). En s’appuyant sur des calculsDFT, des mécanismes de sorption expliquant cette sélectivité ont été proposé. Ainsi le Pd et leNi serait retenu par chélation via deux groupements P=O, le Cu via des groupements P=O et N.La mise en oeuvre du MP-102 au sein d’un procédé couplant la sorption et la filtration aégalement été étudiée afin d’évaluer le comportement du polymère en régime pseudo-continu.Celui-ci maintient ces performances de sélectivité vis-à-vis du Pd (90%) quelque soit le pH et sacapacité de sorption atteint 0,6 mmol/g à pH 3 tout en restant réversible

Ultrafast dynamics in iron tetracarbonyl olefin complexes investigated with two-dimensional vibrational spectroscopy

The dynamics of iron tetracarbonyl olefin complexes has been investigated using two-dimensional infrared (2D-IR) spectroscopy. Cross peaks between all CO-stretching bands show that the CO-stretch modes are coupled, and from the cross-peak anisotropies we can confirm previous assignments of the absorption bands. From the pump-probe delay dependence of the diagonal peaks in the 2D-IR spectrum we obtain a correlation time of [similar]3 ps for the spectral fluctuations of the CO-stretch modes. We observe a multi-exponential pump-probe delay dependence of the cross-peak intensities, with rate constants ranging from 0.1 ps−1 to 0.6 ps−1. To determine whether this delay dependence originates from fluxionality of the complex or from intramolecular vibrational relaxation (IVR), we modulate the free-energy barrier of fluxional rearrangement by varying the pi-backbonding capacities of the olefin ligand in two iron tetracarbonyl olefin complexes: Fe(CO)4(cinnamic acid) and Fe(CO)4(dimethyl fumarate). Since the pi-backbonding strongly influences the rate of fluxionality, comparing the dynamics in the two complexes allows us to determine to what extent the observed dynamics is caused by fluxionality. We conclude that on the time scale of our experiments (up to 100 ps) the cross-peak dynamics in the iron complexes is determined by intramolecular vibrational energy relaxation. Hence, in contrast to previously investigated irontricarbonyl and ironpentacarbonyl complexes, iron tetracarbonyl olefin complexes exhibit no fluxionality on the picosecond time scale