Polyethylene oxide phosphines

Water-soluble polymers, such as polyethylene oxide), can be attached covalently to, e.g., phosphine ligands, to render them water-soluble. Most often this concept has been applied to biphasic catalysis as an alternative to the introduction of ionic water-soluble moieties, such as the sulfonate groups of the archetypical trisulfonat-ed triphenylphosphine (TPPTS cf. Section 3.2.1). 

Polyethylene oxide) and poly(N-alkylacrylamide)s are known to undergo a temperature-dependent phase change whereupon they separate from an aqueous phase at increased temperatures [14]. This inverse temperature dependence, i.e., the occurrence of a lower critical solution temperature, can be related to an entropi-cally favorable decrease in hydrogen bonding between water and the polymer with increasing temperature. In order to exploit this physical property for catalyst recovery, Bergbreiter et al. attached phosphines covalently to commercially available PEO or PEO-b-PPO-b-PEO block copolymers [Schemes 1 and 2 PPO = polypropylene oxide)] [9a],... 

In most cases the catalytically active metal complex moiety is attached to a polymer carrying tertiary phosphine units. Such phosphinated polymers can be prepared from well-known water soluble polymers such as poly(ethyleneimine), poly(acrylic acid) [90,91] or polyethers [92] (see also Chapter 2). The solubility of these catalysts is often pH-dependent [90,91,93] so they can be separated from the reaction mixture by proper manipulation of the pH. Some polymers, such as the polyethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) block copolymers, have inverse temperature dependent solubility in water and retain this property after functionalization with PPh2 and subsequent complexation with rhodium(I). The effect of temperature was demonstrated in the hydrogenation of aqueous allyl alcohol, which proceeded rapidly at 0 °C but stopped completely at 40 °C at which temperature the catalyst precipitated hydrogenation resumed by cooling the solution to 0 °C [92], Such smart catalysts may have special value in regulating the rate of strongly exothermic catalytic reactions. 

Table 4.7. Polyethylene oxide)-substituted phosphine ligands in rhodium-catalyzed hydroformylation ...

Iridium complexes with triphenylphosphine modified with poly(ethylene oxide)s 14 at one of the phosphine groups were active in two-phase hydrogenation of allylbenzene, although the catalyst activity and selectivity with respect to the hydrogenation product, propylbenzene, was substantially lower than in the case of its low molecular analogue and one of the main products was propenylbenzene. Similar results were obtained for an iridium complex with polyethylene oxide modified with pyridyl groups [53],... 

These workers used double extraction chromatography with Microthene-210 (microporous polyethylene) supporting tri- -octyl-phosphine oxide (TOPO) a technique that has been used previously to isolate plutonium from other biological and... 

In contrast to stabilizers, fire retardants must be added in much higher concentrations, which affect thermal and mechanical properties as well as cost. Sherr and co-workers report that novel derivatives of phosphine oxides, phosphonic acids, phosphinic acid, and phosphonium halides may be used generally in concentrations as low as 2.5-5 p.p.h. to be effective fire retardants in polyethylene and poly (methyl methacrylate). 

In our studies we found that phosphonic acids (16), phosphinic acids (25), and phosphine oxides (17) are additives capable of imparting fire retardant properties to thermoplastic polymers. Tables I and II present data for some of these compounds when added to polyethylene or to poly (methyl methacrylate). The concentration reported is not necessarily the lowest effective concentration for the additive in the polymer. These additives also were effective in other thermoplastic polymers such as polystyrene, impact polystyrene, polypropylene and ABS. The compounds were completely compatible with the polymers. 

Dicyclohexylphosphine oxide would thermally disproportionate into dicyclohexylphosphinic acid and dicyclohexylphosphine. We found that both the phosphine oxide, m.p. 72°-75°C., at 15%, and the phosphinic acid, m.p. 144°-145°C., at 5%, in polyethylene are flame retardants. 

Amphiphilic resin-supported ruthenium(II) complexes similar to those shown in Structure 3 (cf. also Section 7.5) were employed as recyclable catalysts for dime-thylformamide production from supercritical C02 itself [24], Tertiary phosphines were attached to crosslinked polystyrene-polyethylene glycol) graft copolymers (PS-PEG resin) with an amino groups to form an immobilized chelating phosphine. Catalytic activity declined with each subsequent recycling step, probably due to oxidation of the phosphines and to metal leaching. 

The oxidation-reduction method, developed initially by Mukaiyama et al. [133] and related to the previously described organophosphorus methods, has permitted a variety of important solid-phase applications. The mechanism of the activation is complex and involves the oxidation of the triaryl/ alkyl-phosphine to the oxide as well as reduction of the disulfide to the mercapto derivative. However, different active species, such as 81 (Fig. 11), the 2-pyridyl thioester, or even the symmetrical anhydride, have been postulated to form. For the intermediate 81, the peptide bond formation may proceed through a (cyclic transition state. The method has been used for conventional stepwise synthesis [134], acylation of the first protected amino acid to a hydroxymethyl resin, and to achieve segment condensation on a solid support in the opposite direction (N C) [135,136]. Lastly, it has been used for efficient grafting of a polyethylene glycol (molecular weight 2000) derivative to an aminomethyl resin to prepare PEG-PS resins [137]. 

Hydrogenated tallow amide Isopropanolamlne Polyethylene glycol PPG-20 Tris [1-(2-methyl-azlrldlnyl) phosphine oxide] rubber processing chemical synthesis 6-t-Butyl-m-cresol rubber processing, synthetic 1-Decanethiol 1-Hexadecanethiol 1-Hexanethiol 1-Octadecanethiol 1-Tetradecanethiol rubber reclaiming... 

Stackman [29] carried out a study to find systems suitable for reducing the flammability of polyethylene terephthalate (PET) and poly-1,4-butylene terephthalate (PBT) while retaining the chemical and physical properties of the original polymers. The additives used were phosphine oxides, phosphonates and phosphates and their activity was assessed by means of an oxygen index test. Most of the phosphorus esters were found to be volatile under the blending conditions and both the halogenated phosphorus esters and halogenated derivatives of phosphorus oxide proved to be ineffective as flame retardants. 

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