Syntheses and rearrangements of tris(hydroxymethyl)phosphine and tetrakis(hydroxymethyl)phosphonium salts

Revisiting the phosphonium salt chemistry for P-doped carbon synthesis: toward high phosphorus contents and beyond the phosphate environment

The introduction of phosphorus and nitrogen atoms in carbo-catalysts is a common way to tune the electronic density, and thereby the reactivity, of the material, as well as to introduce surface reactive sites. Numerous environments are reported for the N atoms, but the P-doping chemistry is less explored and focuses on surface POx groups. A one-step synthesis of P/N-doped carbonaceous materials is presented here, using affordable and industrially available urea and tetrakis(hydroxymethyl)phosphonium chloride (THPC) as the N and P sources, respectively. In contrast to most of the synthetic pathways toward P-doped carbonaceous materials, the THPC precursor only displays P-C bonds along the carbon backbone. This resulted in unusual phosphorus environments for the materials obtained from direct thermal treatment of THPC-urea, presumably of type C-P-N according to 31P NMR and XPS. Alternatively, the in situ polymerization and calcination of the precursors were run in calcium chloride hydrate, used as a combined reaction medium and porogen agent. Following this salt-templating strategy led to particularly high phosphorus contents (up to 18 wt%), associated with porosities up to 600 m2 g-1. The so-formed P/N-doped porous materials were employed as metal-free catalysts for the mild oxidative dehydrogenation of N-heterocycles to N-heteroarenes at room temperature and in air.

β-Cyclodextrin network crosslinked by novel phosphonium-based tetrakiscarboxylic acid derived from PH3 tail gas: Synthesis and application for rapid removal of organic dyes from wastewater

Organic dyes, such as methyl orange (MO), Congo red (CR), crystal violet (CV) and methylene blue (MB), are common organic pollutants existing in wastewater. Therefore, the exploration of bio-based adsorbents for the efficient removal of organic dyes from wastewater has gained many attentions. Here, we report a PCl₃-free synthetic method for the synthesis of phosphonium-containing polymers, in which the prepared tetrakis(2-carboxyethyl) phosphonium chloride-crosslinked β-cyclodextrin (TCPC-β-CD) polymers were applied to the removal of dyes from water. The effects of contact time, pH (1-11), and dye concentration were investigated. The selected dye molecules could be captured by the host-gest inclusion of β-CD cavities, and the phosphonium and carboxyl groups in the polymer structure would respectively facilitate the removal of cationic dyes (MB and CV) and anionic dyes (MO and CR) via electrostatic interactions. In a mono-component system, over 99 % of MB could be removed from water within the first 10 min. Based on the Langmuir model, the calculated maximum adsorption capacities of MO, CR, MB, and CV were 180.43, 426.34, 306.57, and 470.11 mg/g (or 0.55, 0.61, 0.96 and 1.15 mmol/g), respectively. Additionally, TCPC-β-CD was easily regenerated using 1 % HCl in ethanol, and the regenerative adsorbent still showed high removal capacities for MO, CR, and MB even after seven treatment cycles.

The Backbone of Success of P,N-Hybrid Ligands: Some Recent Developments

Organophosphorus ligands are an invaluable family of compounds that continue to underpin important roles in disciplines such as coordination chemistry and catalysis. Their success can routinely be traced back to facile tuneability thus enabling a high degree of control over, for example, electronic and steric properties. Diphosphines, phosphorus compounds bearing two separated P^III donor atoms, are also highly valued and impart their own unique features, for example excellent chelating properties upon metal complexation. In many classical ligands of this type, the backbone connectivity has been based on all carbon spacers only but there is growing interest in embedding other donor atoms such as additional nitrogen (–NH–, –NR–) sites. This review will collate some important examples of ligands in this field, illustrate their role as ligands in coordination chemistry and highlight some of their reactivities and applications. It will be shown that incorporation of a nitrogen-based group can impart unusual reactivities and important catalytic applications.

Martin's Phosphino-Triol Revisited: Unexpected P-C Bond Cleavage Reactions and Their Suppression via Complexation of Al3+ and Sc3

A revised synthesis of Martin's phosphino-triols (two derivatives) is reported. Once isolated, these thermally sensitive triols were shown to disassemble selectively via an unexpected P-C bond cleavage reaction. This degradation pathway was effectively suppressed via complexation of Al³⁺ and Sc³⁺. In the resulting half-cage complexes, the ligand scaffold is bound to each metal (Al³⁺ and Sc³⁺, respectively) via all four donor atoms. So far, this κ⁴-P,O,O',O″-coordination mode has not been observed for any other phosphino-triol.