Styrene complexes

Styrene is manufactured from ethylbenzene. Ethylbenzene [100-41-4] is produced by alkylation of benzene with ethylene, except for a very small fraction that is recovered from mixed Cg aromatics by superfractionation. Ethylbenzene and styrene units are almost always installed together with matching capacities because nearly all of the ethylbenzene produced commercially is converted to styrene. Alkylation is exothermic and dehydrogenation is endothermic. In a typical ethylbenzene—styrene complex, energy economy is realized by advantageously integrating the energy flows of the two units. A plant intended to produce ethylbenzene exclusively or mostly for the merchant market is also not considered viable because the merchant market is small and sporadic. 

Zeolite frameworks, 29, 103 Zirconacarboranes, 306 Zirconium diazametallacycles, 252-255 Zirconium f/ -styrene complexes, 255 Zirconium trimethylenemethane complexes, 256-257... 

In an attempt to combine the syndioselectivity of half-sandwich titanium catalysts with the living characteristics of anionic polymerization initiators, the use of half-sandwich calcium-based catalysts has been described.363 364 In neat styrene complex (152) affords 76% rr triad PS. However, polydispersities are still quite high (Mw/Mn > 2.2)... 

Figure 9. Two views of Fu s bis(azaferrocene) CuOTf-styrene complex. [Adapted from (64).]...

Figure 11. X-ray crystal structure of Jacobsen s diimine-copper styrene complex (116) showing aromatic face-face and edge-face interactions (PF6 counterion and some hydrogen atoms omitted for clarity). [Adapted from (62).]...

Ethylbenzene plants, 23 330-331 Ethylbenzene-styrene complex, 23 328 Ethylbenzene synthesis molecular sieves in, 16 845 zeolite-based alkylation in, 23 331-333 Ethyl benzoate, 3 635 Ethyl P-D-glucopyranoside, 4 701 7-Ethylbicyclooxazolidine, antimicrobial used in cosmetics, 7 831t Ethyl bromide, physical properties of, 4 351t... 

Complexes 53 are efficient catalysts for the homodimerization of 1-octene and styrene. Complex 53a bearing the sterically more demanding l,3-bis(2,6-diisopropylphenyl)-NHC ligand shows a higher reactivity than the mesityl-substituted 53b. These complexes also catalyze the CM of 1-octene or styrene with methyl acrylate ( 80% yield), the RCM of diethyl diallylmalonate at 40 °C ( 95% yield), and the ROMP of cyclooctene at 60 °C ( 90% yield). By GC-MS analysis the presence of free p-cymene was detected in the beginning of the reactions. From these results it may be concluded that the first step of the catalytic cycle is arene decoordination to generate a 12-electron [OsCl(= CHPh)(NHC)] + derivative as the catalytically active species [102],... 

The methyl esters of (/ )- or (5)-pyrrolidone-5-carboxylic acid (acronym mepy) respectively form [Rh2(5/ -mepy)4] or [Rh2(55-mepy)4] complexes (see Structure 8). The catalyst is thus available in both configurations, 5R or 5S. Such catalysts deliver often more than 90% ee and conformational energy minima (extended Hiickel) of the carbene-styrene complex predict the observed enantiomer preference [24 a]. 

The copolymerization of CD-complexed styrene and DEF led to a precipitation of the corresponding water-insoluble copolymers [43], The reactivity of the styrene complex is higher than that of complexed DEF. The conversions of both monomers were finished after about 6 h at room temperature. The lower reactivity of DEF in comparison to styrene can be explained by the fact that the double bond is sterically hindered by the two ester groups in the trans-1,2 position (Fig. 9). 

Of course, if the only polymerizations performable were those of styrene, complex bases would be of little interest in the anionic polymerization field. 

Another aqueous heterogeneous polymerization was recently reported for the precipitation polymerization of MMA and styrene complexed with methylated /3-cyclodextrin.256 The polymerization was carried out in water with 1-21 (X = Br)/CuBr/L-4 to give polymers with controlled molecular weights and relatively narrow MWDs (MJMn = 1.3—1.8). Initially, the reaction mixture was homogeneous with the hydrophilic cyclodextrin-complexed MMA, but sooner or later it became heterogeneous due to the formation of water-insoluble polymers. 

Following irradiation of a mixture of triarylstibines and styrenes, air oxidation gives the 2-aryl-1-phenylethanols (81 R = H, Me) in a transformation which has been rationalised in terms of valence expansion of the oxygen-antimony-styrene complex and subsequent reductive coupling. 

Aryl-l-phenylethanol derivatives (378) are formed from the irradiation of styrenes (379) with triarylstibines (380) in the presence of oxygen. The yields of the products are modest (14-48%) and the mechanism for product formation involves a stibine/oxygen/styrene complex (381) which reportedly undergoes valence expansion to (382) followed by rearrangement to (383) and hydrolysis to yield the isolated alcohols. 

The first stage of waste heat recovery is used to superheat the EB and the primary steam. Subsequent stages are used to generate steam at different pressures. Typically intermediate pressure steam and low pressure steam are generated, which are directed for use elsewhere in the styrene plant or larger EB-styrene complex. 

The alkylation and transalkylation reactor effluent streams are sent to the distillation section, which consists primarily of three fractionation columns. The first column is a benzene column, which separates unconverted benzene into the overhead stream for recycling to the reactors. The benzene column bottom stream feeds the EB column. The EB column recovers the EB product in the overhead stream, and the bottom stream of the EB column feeds the PEB column where PEB is fractionated overhead and recycled to the transalkylation reactor. The bottom stream of the PEB column is removed as a residue stream and is generally used as fuel in an integrated styrene complex. 

Analogously a four coordinate styrene complex Ru(Ti"-CH2=CHPh)2(PPh3)2 has been known, though one of the styrene ligands has an rf character [142]. 

Gustorf and co-workers (264-266) have prepared complexes of the type (7r-CH2=CHX)Fe(CO)4 [X = OCOCH3 (266), Cl, CH3, CeHs, or OCH3 (265)] by irradiation of Fe(CO)5 with the corresponding olefin. The complexes are very oxygen-sensitive and thermally unstable. At room temperature they decompose to yield the olefin and Fe3(CO)i2. The order of thermal stability is vinyl chloride > styrene > propylene > vinyl methyl ether. The vinyl chloride and styrene complexes show catalytic activity for polymerization of methyl methacrylate in the presence of a small amount of halogenated hydrocarbon, e.g., CCI4, at room temperature (265). 

Bercaw has extended these studies of alkyl formation from niobium olefin-hydride complexes to include additional examples of meta-substituted styrene complexes of permethylniobocene. As noted in earlier work , electron-donating substituents on the j8-carbon accelerate this insertion reaction, whereas electron-withdrawing substituents retard the rate based on a correlation with a p of —1.2... 

Many carbanions react with [Fp(olefin)] complexes to form relatively stable / -alkyliron complexes. Stabilized enolates derived from cyanoacetates, ma-lonates, acetoacetates and nitromethane react with the [Fp(styrene)]" complex almost exclusively at the benzylic carbon but react with [Fp(propene)] complexes with low regioselectivity ... 

Under standard catalytic conditions (10% PdCh, 1 eq. CuCI, O2, in DMF/H2O), the Wacker oxidation of 4-methoxystyrene proceeded to give a mixture of the two possible products. As expected, the Markovnikov product, methylketone 31 was predominate and only a small amount of aldehyde 30 was isolated (31 30 = 8.4 1). However, Spencer and coworkers performed the reaction in the absence of the reoxidant CuCI and observed a reversal of the usual regioselectivity.26 Thus, reaction of 4-methoxystyrene with 2 equivalents of PdCb gave aldehyde 30 as the major product. The authors explained the regioselectivity by the involvement of a possible 4-palladium-styrene complex 29. 

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