Acrylonitrile metal complexes

Acoustic emission diazine metal complexes, 80 Acrylonitrile metal complexes, 263 Actinide complexes cupferron, 510 dimethyl sulfoxide IR spectra, 490 phosphines SHAB theory, 1040 phthalocyanines, 864 thiocyanates, 236 Actins, 973 Acylates H3-ligands... 

Substances satisfying these conditions are colorless and do not absorb in the high-wavelength range. It is possible to classify them according to their chemical structure as derivatives of 2-hydroxybenzophenone, esters of aromatic acids and aromatic alcohols, hydroxyphenyl-benzotriazoles, substituted acrylonitriles, metallic complexes (excited-state quenchers), and inorganic pigments [4,9,23,26,27]. 

Many of these systems employ charged polymers or polyelectrolytes that confer on them particular properties due to the existence of electrical charges in the polymer structure. Oyama and Anson [14,15] introduced polyelectrolytes at electrode surfaces by using poly(vinylpiridine), PVP, and poly-(acrylonitrile) to coordinate metal complexes via the pyridines or nitrile groups pending from the polymer backbone. Thomas Meyer s group at North Carolina [16, 17[ also employed poly(vinylpyridine) to coordinate Ru, Os, Re and other transition-metal complexes by generating an open coordination site on the precursor-metal complex. 

The last decades have witnessed the emergence of new living Vcontrolled polymerizations based on radical chemistry [81, 82]. Two main approaches have been investigated the first involves mediation of the free radical process by stable nitroxyl radicals, such as TEMPO while the second relies upon a Kharash-type reaction mediated by metal complexes such as copper(I) bromide ligated with 2,2 -bipyridine. In the latter case, the polymerization is initiated by alkyl halides or arenesulfonyl halides. Nitroxide-based initiators are efficient for styrene and styrene derivatives, while the metal-mediated polymerization system, the so called ATRP (Atom Transfer Radical Polymerization) seems the most robust since it can be successfully applied to the living Vcontrolled polymerization of styrenes, acrylates, methacrylates, acrylonitrile, and isobutene. Significantly, both TEMPO and metal-mediated polymerization systems allow molec-... 

Besides formaldehyde, Michael acceptors such as acrylonitrile and ethyl acrylate also serve as substrate to undergo the addition in the presence of various metal complexes [10-14]. Acrylonitrile affords P(CH2CH2CN)3 tcep (Scheme 3). The order of catalytic activity is reported to be Pt[P(CH2CH2CN)3]3>Pd[P(CH2CH2CN)3]3P IrCl[P(CH2CH2CN)3]3>Ni[P(C-H2CH2CN)3]3. The solvent effect on the rate is not significant. In acetonitrile, however, a small amount of a telomer is formed. 

The first investigations on iron-catalyzed Michael reactions utilized Fe(acac)3 as catalyst. However, this metal complex is itself catalytically almost inactive. Yields of only up to 63% could be achieved, if BF3OEt2 is used as a co-catalyst [55], Polystyrene-bound Fe(acac)3 catalysts were also reported to give yields up to 63% [56], FeCl3 was used as a co-catalyst for clay-supported Ni(II). Yields achieved with this heterogeneous system ranged from 40 to 98% [57]. The double Michael addition of acrylonitrile to ethyl cyanoacetate is smoothly catalyzed by a complex generated from [Fe(N2) (depe)2] [depe = l,2-bis(diethylphosphano)ethane]. At 23 °C and after 36h, an 88% yield is obtained with 1 mol% of this Fe(0) catalyst [58]. 

Kundig and coworkers have reported the Baylis-Hillman-reaction of methyl acrylate and acrylonitrile with planar chiral arylaldimine tricarbonylchromium complexes, such as 19 (Scheme 4) [28]. These reactions proceeded by attack of the acrylate from the sterically less encumbered site of the metal complex and afforded the products 21 with very good diastereoselectivity. 

Although ethers have been used less frequently than alcohols, it has recently been reported that tetrahydrofuran (THF) is photocatalytically activated by TBADT, and the alkylation of unsaturated nitriles is obtained in good yield [15]. As an alternative, the C—Br bond in various glycosyl bromides has been homolytically cleaved, and the resulting radical trapped by acrylonitrile to form the corresponding C-glycosides. The halogen abstraction step is initiated by a photolabile iron-based dimeric metal complex [16]. 

Section 6.4.4 already presented several examples of photocatalysts such as metalloporphyrins and other organic metal complexes. In another example, a singlet excited photocatalyst, 1,4-dicyanonaphthalene (DCN), initiates the photochemical electron transfer-induced ring opening of an azirine 568 (Scheme 6.272).1473 Subsequent addition of an intermediate 569 to acrylonitrile leads to 570 in two steps, while DCN is regenerated.883... 

Living polymerization of lactones has been successfully performed by the catalysis of rare earth metal complexes producing Mw/Mn values of 1.07-1.08 [5]. Polymerizations of acrylonitrile and alkyl isocyanates have been successfully realized using La[CH(SiMe3)2]2(C5Me5) as initiator, and those of various oxiranes have been made using Ln(acac)3/AlR3/H20 system [6]. 

Late transition-metal complexes can also polymerize nonpolar and polar comonomers, such as alkyl acrylates, acrylonitrile, or carbon monoxide. Polyketones have been efficiently produced through CO-ethylene copolymerizations [46],... 

A number of transition metal complexes have been apphed in ATRP process. It has been successful for molybdenum, chromium, rhenium, ruthenium, and iron, rhodiiun, nickel, palladium, and copper complexes. Among these, copper catalysts are superior in terms of versatihty and cost. Styrenes, (meth)acrylates, (meth)acrylamides, and acrylonitrile have been successfully polymerized using copper-mediated ATRP. The polymerization has been foimd to be tolerant to a variety of... 

In the presence of transition metal complexes, certain strained hydrocarbon systems are activated under mild thermal conditions and undergo characteristic transformations. Methylenecyclopropane (XXVI) (Noyori et al., 1970, 1972b), bicyclo[2.1.0]pentane (XXVII) (Noyori et al., 1971c, 1974a), and quadricyclane (XXVIII) (Noyori et al., 1975a) add to electron-deficient olefins with the aid of a nickel(0) catalyst such as bis(l,5-cyclooctadiene)-nickel(O) or bis(acrylonitrile)nickel(0). These cycloaddition reactions proceed... 

Osborn s group has continued its studies on whether alkyl halides add oxidatively to iridium(I) compounds by a radical chain or an S 2 mechanism by using more reactive metal complexes such as [Ir(PMe3)2(CO)Cl]. For simple alkyl (methyl excepted), vinyl, and aryl halides and a-halo-esters, evidence based on the effect of radical initiators and inhibitors, structure-reactivity relationships, the trapping of radicals by acrylonitrile, and the loss of stereospecificity at the reacting carbon atom all indicate a radical chain process, perhaps as in equations (14) and (15) ... 

The hydration of C-C multiple bonds is a reaction with prevalent industrial interest due to the usefulness of the products as chemical intermediates. The wool-Pd complex is an economical and highly active catalyst for hydration of olefins. It is very stable and can be reused several times without any remarkable change in the catalytic activity [73, 74]. In particular, to convert alkenes to the corresponding alcohols in excellent enantioselectivity, a new biopolymer-metal complex constituted of wool-supported palladium-iron or palladium-cobalt was prepared and used, such as allylamine to amino-2-propanoI, acrylonitrile to lactonitrile and unsaturated acids to a-hydroxycarboxylic acids [75-77]. The same catalytic system was also used for hydration of substituted styrenes to produce chiral benzyl alcohols. The simple and cleaner procedure, mild reaction conditions, high stability and recovery rate of catalyst made these catalytic systems an attractive and useful alternative to the existing methods (Scheme 37). 

MAA and MMA may also be prepared via the ammoxidation of isobutylene to give meth acrylonitrile as the key intermediate. A mixture of isobutjiene, ammonia, and air are passed over a complex mixed metal oxide catalyst at elevated temperatures to give a 70—80% yield of methacrylonitrile. Suitable catalysts often include mixtures of molybdenum, bismuth, iron, and antimony, in addition to a noble metal (131—133). The meth acrylonitrile formed may then be hydrolyzed to methacrjiamide by treatment with one equivalent of sulfuric acid. The methacrjiamide can be esterified to MMA or hydrolyzed to MAA under conditions similar to those employed in the ACH process. The relatively modest yields obtainable in the ammoxidation reaction and the generation of a considerable acid waste stream combine to make this process economically less desirable than the ACH or C-4 oxidation to methacrolein processes. 

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