Metal phosphonates, applications

The selective intercalation of guests into solid hosts offers the potential for application in catalysis and separation science. An excellent case in point is zeolites, which exhibit shape and size selective inclusion properties and are used for an enormous variety of processes [44,45]. Additionally, a munber of layered materials have been reported to possess selective intercalation properties, including layered metal phosphonates [46,47], montmorUlonite [48], magnesium aluminum oxide [49], and layered double hydroxides [50-59]. 

Some Applications of Layered and Pillared Metal Phosphonates.. 153... 

The metal phosphonate compounds usually adopt layered or pillared layered structures with the organic moieties filling in the inter-layer spaces [1-4]. The layered nature makes them interesting candidates to host intercalation reactions. Furthermore, the potential for the organic moieties to be modified by functional groups allows for the preparation of a number of new materials that have possible applications in areas such as catalysis, ion exchange, sensing and ion conduction [1,4-7]. 

In certain cases, self-assembly methods can be employed to prepare multilayered thin films analogous to LB films. Typically, once the surface has been primed with a molecular adhesion layer, subsequent layers are assembled in a layer-by-layer fashion where the end group of the previously deposited layer directs the assembly of the next layer. Strong electrostatic or covalent interactions between the layers serve to stabilize the assemblies. The most notable examples of self-assembled multilayered films are those based upon metal phosphonates [21]. Although these multilayers are structurally analogous to LB films, their thermal and solvent stability makes them potentially more useful in many applications, including electron-transfer studies. 

In the oxide literature, there are several reviews specific to the different families, such as layered transition metal oxides and metal phosphonates. Synthesis of metal nitrides has been discussed by Di Salvo. Precursor synthesis of oxides, chalcogenides and other materials is being pursued with vigour. - Thus, single-molecule precursors of chalcogenide containing compound semiconductors have b n developed. Kanatzidis has reviewed the application of molten poly-chalcophosphate fluxes for the synthesis of complex metal thiophosphates and selenophosphates. 

As conclusion, bifunctional fibers having both phosphonic acid and sulfonic acid groups exhibit the characteristic metal ion selectivity and high breakthrough capacities in addition to the extremely fast adsorption rates. Studies on behavior of FPS-f in adsorption of other heavy metals like Fe(III) are now in progress. The bifunctional fiber developed in this work is attractive to application to the protection of the environment because of its extremely rapid adsorption rates and characteristic metal ion selectivity. 

Layered metal IV phosphonates are widely used, particularly zirconium phosphonates, because their synthesis is versatile and their structural arrangement may be tailored to applications. Zirconium phosphonates are usually prepared by heating an aqueous solution of a metal IV salt (e.g., ZrOCl2) with a phosphonic acid at 60-80 °C synthesis in the presence of HP permits one to increase significantly the crystallinity of the final products. 

Saccharidic Difluorophosphonates Difluoromethylene phospho-nates have been the focus of numerous works. Indeed, these compounds are able to mimic the phosphate bond in the synthesis of enzyme inhibitors. This interest is obvious for the furanose series in this case, they are non scissible analogues of 5-phosphate nucleosides (cf. Chapter 7). Difluoromethylene phosphonates can be prepared via a radical path starting from compounds that have the difluoromethylene moiety in the pseudo-anomeric position. Nevertheless, methods based on metal derivatives of difluorophosphonates are generally easier and broadly applicable. 

Table 10.7 summarizes the application work. It was found that EDDS increased the peracid stability when used in combination with all three phosphonates, gave enhanced dye protection, and was roughly comparable on stain removal. The most surprising result was the EDDS-HEDP combination [38], which delivered the highest and most stable peracid release, best stain removal, and best dye protection despite the very poor performance of HEDP alone. This may be explained by the opposite preference of EDDS and HEDP for metal ions at alkaline pH. HEDP seems only to complex with hardness ions and this appears to increase the selectivity of E D D S for transition metal ions by reducing the hardness ions available to bind with EDDS. 

Functionalized polymers are of interest in a variety of applications including but not limited to fire retardants, selective sorption resins, chromatography media, controlled release devices and phase transfer catalysts. This research has been conducted in an effort to functionalize a polymer with a variety of different reactive sites for use in membrane applications. These membranes are to be used for the specific separation and removal of metal ions of interest. A porous support was used to obtain membranes of a specified thickness with the desired mechanical stability. The monomer employed in this study was vinylbenzyl chloride, and it was lightly crosslinked with divinylbenzene in a photopolymerization. Specific ligands incorporated into the membrane film include dimethyl phosphonate esters, isopropyl phosphonate esters, phosphonic acid, and triethyl ammonium chloride groups. Most of the functionalization reactions were conducted with the solid membrane and liquid reactants, however, the vinylbenzyl chloride monomer was transformed to vinylbenzyl triethyl ammonium chloride prior to polymerization in some cases. The reaction conditions and analysis tools for uniformly derivatizing the crosslinked vinylbenzyl chloride / divinyl benzene films are presented in detail. 

Apart from their behaviour as ligands in metal catalyst systems, studies of the reactivity of phosphites towards a wide variety of other substrates have attracted attention. New aspects and applications of the classical Michaelis-Arbuzov reaction and its variants continue to appear. Evidence of the thermal disproportionation of methyltriaryloxyphosphonium halides formed in the reactions of triarylphosphites with alkyl halides, together with the formation of P-O-P intermediates, has been reported. The Michaelis-Arbuzov reaction has been used in the synthesis of phosphonate-based styrene-divinylbenzene resins and polyphosphonated chelation therapy ligands.Treatment of electron-rich benzylic alcohols dissolved in triethylphosphite with one equivalent of iodine affords a low-temperature one-pot route to the related benzylic phosphonates, compounds which are otherwise difficult to prepare. Upper-rim chloromethylated thiacalix[4]arenes have also been shown to undergo phosphonation on treatment with a phosphite ester in chloroform at room temperature. The nickel(II)-catalysed reaction of aryl halides with phosphite esters in high boiling solvents, e.g., diphenyl ether, (the Tavs reaction), has also... 

The metal (zinc, nickel, etc.) dithiophosphonates are attractive antioxidants in lubricants and plastics,124,125 and vulcanization accelerators (more active than analogous dithiophosphates).126 Many metal dithiophosphonates can be extracted with organic solvents and this property can be exploited for analytical applications, e.g., for copper(II) and bismuth(III) (O-hexyl)butyldithio-phosphonates,127 nickel(II), cobalt(II), and palladium(II) (0-ethyl)methyldithiophosphonates,128 platinum(IV), palladium(II), and gold(III) (O-ethyl)methyldithiophosphonates,129 and noble and rare metal (O-methyl)methyldithiophosphonates.130... 

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