Poly —Wilkinson

This is a reasonable inference, because site binding is significant only with multivalent cations and strong electrostatic interactions. Under these conditions ion polarization occurs and bonds have some covalent character (Cotton Wilkinson, 1966). This is illustrated by the data of Gregor, Luttinger Loebl (1955a,b). They measured the complexation constants of poly(acrylic acid), 0 06 n in aqueous solution, with various divalent metals, which, as it so happens, are of interest to AB cements (Table 4.1). The order of stability was found to be... 

The mechanism of the intracellular degradation of poly(HA) by bacteria, i.e., the mobilization of a previously accumulated polyester, is poorly understood (see also the chapter by Babel et al. in this book). Most of the research on intracellular poly(3HB) mobilization was done more than 30 years ago. Lemoigne observed in 1925 that 3-hydroxybutyrate was the main product of anaerobic breakdown of poly(3HB) in Bacillus M [12,137]. Macrae and Wilkinson [138, 139] noticed a reduction of the poly(3HB) content of Bacillus megaterium upon aerobic incubation of poly(3HB)-rich cells in phosphate buffer. The authors found that autolysis of poly(3HB)-rich cells occurred later and to a minor extent compared to poly(3HB)-poor cells and proposed that poly(3HB) might... 

In this paper we describe the reaction of poly(methyl methacrylate), PMMA, and red phosphorus and use that information to predict that the reaction of Wilkinson s catalyst, CIRh(PPh3)3, and PMMA may be a worthwhile investigation. Finally information from this reaction is utilized to identify other potential additives and the reaction of these cobalt compounds with PMMA is described. Part of the strategy that will be explored is a strategy of cross-linking to produce materials with greatly increased thermal stability. 

Work with supported ionic liquids was extended to a cationic polymer, poly (diallyldimethylammonium chloride), which has quaternary ammonium functional groups (Fig. 16) 268). The extra-structural counter anion is Cl . The polymer was applied to simultaneously incorporate an ionic liquid and a transition-metal catalyst via a simple mixing of the components. Wilkinson s catalyst and [BMIM]PF6 were... 

Table 1. Reversible solubility of various fluorinated compounds in C02-expanded liquids at 25°C. PFPE = poly(hexafluoropropyleneoxide) Fl-Wilkinson s Catalyst RhCKPR,), with R = C6H4-P-CH2CH2C6F13 (D-...

Niven, R.W., F. Rypacek, and P.R. Byron. 1990. Solute absorption from the airways ofthe isolated rat lung. III. Absorption of several peptidase-resistant, synthetic polypeptides poly-(2-hydroxyethyl) -as-partamides. Pharm. Res. 7 990-994. Hoover, J.L., B.D. Rush, K.F. Wilkinson, J.S. Day, P.S. Burton,T.J. Vidmar, and M.J. Ruwart. 1992. Peptides are better absorbed from the lung than the gut in the rat. Pharm. Res. 9 1103-1106. 

Generally, Wilkinson complexes which are coordinated with polymeric legands show a relatively high stability in reactions. This is explained as a contribution of the hydrophobic environment of the polymer (113,114). Besides, the polymer plays a role of holding metal without its coagulation. Poly(naphtoquinone)-K-FeCl3 in the ammonia synthesis (115) and poly(acrylic acid)-Rh(III) in the hydrogenation are shown as examples (116,117). 

Continuous homogeneous catalysis is achieved by membrane filtration, which separates the polymeric catalyst from low molecular weight solvent and products. Hydrogenation of 1-pentene with the soluble pofymer-attached Wilkinson catalyst affords n-pentane in quantitative yield A variety of other catalysts have been attached to functionalized polystyrenes Besides linear polystyrenes, poly(ethylene glycol)s, polyvinylpyrrolidinones and poly(vinyl chloride)s have been used for the liquid-phase catalysis. Instead of membrane filtration for separating the polymer-bound catalyst, selective precipitation has been found to be very effective. In all... 

Poli, R. Wilkinson, G. Montevalli, M. Hurst-house, M.B. J. Chem. Soc., Chem. Commun. 

Supported ionic hquid phase hydrogenation catalysts based on a polymeric poly(aUyldimethylammonium chloride) support have also been prepared by attachment of [BMIM][PF6] solutions of [RhQ(PPh3)3] (Wilkinson... 

The potential of microemulsions for organometaUic-catalyzed hydrogenations in water/scC02 biphasic systems has been assessed using the rhodium-catalyzed hydrogenation of styrene as a common test reaction [Eq. (7)] [31]. The water-soluble Wilkinson complex [RhCl(TPPTS)3] was applied as catalyst precursor together with anionic perfluoropolyether carboxylates, cationic Lodyne A, or nonionic poly-(butene oxide)-b-poly(ethylene oxide) surfactants. The interfacial tension is small in the presence of the supercritical fluid and small amounts of surfactant (0.1-2.0 wt.%) suffice to form stable microemulsions. The droplet diameter of the microemulsions varied between 0.5 and 15 pm and a surface area of up to 10 m was obtained. 

R.M. Macrae, J.F. Wilkinson, Poly-beta-hydroxybutyrate metabolism in washed suspensions of Bacillus cereus and Bacillus megate-rium, J. Gen. Microbiol. 19 (1) (1958) 210-222. 

In 1969, Kern first reported that the Wilkinson catalyst, RhCl(PPh3)3, could be used to polymerize phenylacetylene monomer, and that the color of the resulting poly(phenylacetylene) was dependent on the polymerization conditions used." Recently, analogues of the Wilkinson catalyst such as [(2,5-norbornadiene)RhCl]2 (7, Figure 21.1) have been developed that selectively produce c/ -PPA even at room temperature. This is in contrast to the low temperature (—78 °C) required when using Ziegler-Natta catalysts to produce perfect c/ -polyacetylene." ... 

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