Cationic Phosphinidene as a Versatile P1 Building Block: [LC-P]+ Transfer from Phosphonio-Phosphanides [LC-P-PR3]+ and Subsequent LC Replacement Reactions (LC = N-Heterocyclic Carbene).

Cationic imidazoliumyl(phosphonio)-phosphanides [LC-P-PR3]+ (1a-e+, LC = 4,5-dimethyl-1,3-diisopropylimidazolium-2-yl; R = alkyl, aryl) are obtained via the nucleophilic fragmentation of tetracationic tetraphosphetane [(LC-P)4][OTf]4 (2[OTf]4) with tertiary phosphanes. They act as [LC-P]+ transfer reagents in phospha-Wittig-type reactions, when converted with various thiocarbonyls, giving unprecedented cationic phosphaalkenes [LC-P═CR2]+ (5a-f[OTf]) or phosphanides [LC-P-CR(NR2')]+ (6a-d[OTf]). Theoretical calculations suggest that three-membered cyclic thiophosphiranes are crucial intermediates of this reaction. To test this hypothesis, treatment of [LC-P-PPh3]+ with phosphaalkenes, that are isolobal to thioketones, permits the isolation of diphosphirane salts 11a,b[OTf]. Furthermore, preliminary studies suggest that the cationic phosphaalkene [LC-P═CPh2]+ may be employed to access rare examples of η2-P═C π-complexes with Pd0 and Pt0 when treated with [Pd(PPh3)4] and [Pt(PPh3)3] for which analogous complexes of neutral phosphaalkenes are scarce. The versatility of [LC-P]+ as a valuable P1 building block was showcased in substitution reactions of the transferred LC-substituent using nucleophiles. This is demonstrated through the reactions of 5a[OTf] and 6c[OTf] with Grignard reagents and KNPh2, providing a convenient, high-yielding access to MesP═CPh2 (16) and otherwise difficult-to-synthesize 1,3-diphosphetane 17 and P-aminophosphaalkenes.

Selective Separation of Lithium, Magnesium and Calcium using 4-Phosphoryl Pyrazolones as pH-Regulated Receptors.

Ensuring continuous and sustainable lithium supply requires the development of highly efficient separation processes such as LLE (liquid-liquid extraction) for both primary sources and certain waste streams. In this work, 4-phosphoryl pyrazolones are used in an efficient pH-controlled stepwise separation of Li+ from Ca2+ , Mg2+ , Na+ and K+ . The factors affecting LLE process, such as the substitution pattern of the extractant, diluent/water distribution, co-ligand, pH, and speciation of the metal complexes involved, were systematically investigated. The maximum extraction efficiency of Li+ at pH 6.0 was 94 % when Mg2+ and Ca2+ were previously separated at pH<5.0, proving that the separation of these ions is possible by simply modulating the pH of the aqueous phase. Our study points a way to separation of lithium from acid brine or from spent lithium ion battery leaching solutions, which supports the future supply of lithium in a more environmentally friendly and sustainable manner.

Spatiotemporal Control of Supramolecular Polymerization and Gelation of Metal-Organic Polyhedra.

In coordination-based supramolecular materials such as metallogels, simultaneous temporal and spatial control of their assembly remains challenging. Here, we demonstrate that the combination of light with acids as stimuli allows for the spatiotemporal control over the architectures, mechanical properties, and shape of porous soft materials based on metal-organic polyhedra (MOPs). First, we show that the formation of a colloidal gel network from a preformed kinetically trapped MOP solution can be triggered upon addition of trifluoroacetic acid (TFA) and that acid concentration determines the reaction kinetics. As determined by time-resolved dynamic light scattering, UV-vis absorption, and 1H NMR spectroscopies and rheology measurements, the consequences of the increase in acid concentration are (i) an increase in the cross-linking between MOPs; (ii) a growth in the size of the colloidal particles forming the gel network; (iii) an increase in the density of the colloidal network; and (iv) a decrease in the ductility and stiffness of the resulting gel. We then demonstrate that irradiation of a dispersed photoacid generator, pyranine, allows the spatiotemporal control of the gel formation by locally triggering the self-assembly process. Using this methodology, we show that the gel can be patterned into a desired shape. Such precise positioning of the assembled structures, combined with the stable and permanent porosity of MOPs, could allow their integration into devices for applications such as sensing, separation, catalysis, or drug release.

Ethanol to Aromatics on Modified H-ZSM-5 Part II: An Unexpected Low Coking.

In this study a commercial H-ZSM-5 zeolite (Si/Al=11) was post-synthetically modified by a combined dealumination procedure to adjust its catalytic properties for the selective formation of aromatics from ethanol. The solid-state properties of original and modified zeolites are determined by structural, textural and acidity analysis. The formation of aromatics and durability of the zeolites were investigated depending on space velocity or contact time in the catalyst bed. In particular, the formation rate and desorption of aromatics from solid-state surface as well as their tendency to form coke precursors by consecutive build-up reactions determine the formation of coke. Therefore, the rate of build-up and finished aromatization by hydride transfer (pre-determined by the kind, location and geometric arrangement of surface acid sites) and the statistical number of reaction events until final desorption at the specific contact time have to be harmonized to increase aromatics yield and to decrease catalyst decay by coke simultaneously.