Polystyrenes catalysts

Figure 10.23. Syndiotactic, chain-end controlled polystyrene catalyst...

Polystyrene catalysts /, 1 % to 20% CL with divinylbenzene, have been tested in the reaction of chloride ion with n-decyl methanesulfonate (Eq. (5)) 77). The catalyst... 

Not all nucleophilic displacement reactions require lightly substituted onium ion catalysts for activity. For alkylation of 2-naphthoxide ion with benzyl bromide (Eq. (6)) 40-100% RS, 2% CL polystyrene catalysts 15 and 16 work well54). A 51 % RS catalyst 11 gave good yields in reactions of anionic oxygen and sulfur nucleophiles with alkyl halides 91). 

The nature of the support can have a very profound influence on the catalyst activity. Thus, phosphinated polyvinyl chloride supports are fairly inactive (75), and phosphinated polystyrene catalysts are considerably more active (57), but rather less active particularly when cyclic olefins are the substrates than phosphinated silica supports (76). Silica-supported catalysts may be more active because the rhodium(I) complexes are bound to the outside of the silica surface and are, therefore, more readily available to the reactants than in the polystyrene-based catalysts where the rhodium(I) complex may be deep inside the polymer beads. If this is so, the polystyrene-based catalysts should be more valuable when it is desired to hydrogenate selectively one olefin in a mixture of olefins, whereas the silica-based catalysts should be more valuable when a rapid hydrogenation of a pure substrate is required. 

Pd denotes a phosphinylated polystyrene catalyst -Pd denotes a phos-phinylated silica gel catalyst. 

P)-Pd = phosphinylated polystyrene catalyst 10 7-benzyl-7-azabicyclo[3.2.t]hepl-2-en-6-one yield 65%... 

Pd = phosphinylated polystyrene catalyst (0.018 mol% Pd to substrate) 12 cis-l-henzylumino-2-metltvl-5-isopropenyl-2-cyclohexene... 

Very few nickel-NHC catalysts have been shown to catalyze the polymerization of styrene. In 2005, Shen reported the details of a salicylaldiminato-Ni-NHC complex (64) (Figure 31.13), which is still among the most efficient Ni-NHC polystyrene catalysts known today [94]. Activation of the catalyst with NaBPh4 facilitated the cationic polymerization of styrene in quantitative yield after 12 h at 80 °C in toluene, and afforded a polymer with M of 17.6 kDa and a PDI of... 

The activity of the liquid phase polyhalogenated metalloporphyrins (Co, Mn, Fe) and supported catalysts (silica, polystyrene) and the cationic metalloporphyrins encapsulated in NaX zeolite are founded to be active for cyclooctane oxidation with molecular into ketone and alcohol with primary ketone formation. At the last case the ration c-one/c-ol is higher than at the use supported on silica and polystyrene catalysts and in fact coincide with results, which are received with the cationic metalloporphyrins in solution. [54]. 

Schellenberg, J. Tomotsu, N. Syndiotactic polystyrene catalysts and polymerization. Prog. Polym. Sci. 2002, 27, 1925-1982. 

For comprehensive reviews, see (a) Schellenberg, J., Tomotsu, N. Syndiotactic polystyrene catalysts and polymerization. Prog. Polym. Sci., 27,1925-1982 (2002). (b) Schellenberg, J. Recent transition metal catalysts for syndiotactic polystyrene. Progress Polym. Sci.,34, 688-718 (2009). 

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