CO and a-Olefins

The two stereoregular forms of copolymers generated from CO and substituted olefins. 

The copolymerization of carbon monoxide and propylene confronts issues of both regiochemistry and stereochemistry. The catalyst must control the re osdectivity of the insertion of the a-olefin and the relative and absolute stereochemistry along the main chain. A majority of the studies on the copolymerization of carbon monoxide and substituted olefins have been conducted with styrene and propene as the olefin. The regiochemistiy and steieochemistiy of the copolymerization of carbon monoxide with styrene is distinct from those of the copolymerization of carbon monoxide with propene. These differences result finm differences in the electronic properties of tine olefins and its impact on the regiochemistry for the insertion. The copolymerization of carbon monoxide with styrene is presented first, and tine copolymerization of carbon monoxide with propylene is presented second. 

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Polyketones Obtained by Copolymerisation of CO and a-Olefins in the Presence of Catalysts Containing Pd and Bidentate Phosphine Ligands... 

For the range of industrially relevant conditions, the developed model could accurately predict both the observed CO conversion and the products distribution up to n = 49, in terms of total hydrocarbons, n-paraffins, and a-olefins. In particular, using thirteen adaptive parameters, the model is able to describe the typical deviations of the product distribution from the ASF model, i.e., the methane high selectivity, the low selectivity to C2 species, and the change of the slope of the ASF plot with growing carbon number. Accordingly, the present model can be applied to identify optimized process conditions that are suitable to grant the desired conversion with the requested products distribution. 

Since the direct carbonylation of C-H bonds with CO leading to aldehydes is endothermic, the reaction is conducted under photochemical conditions.109,109a 109e On the other hand, the direct coupling of a C-H bond, CO, and an olefin leading to a ketone is exothermic and can proceed under thermal reaction conditions. 

Aminoacylpalladium complexes, obtained from the reaction between an olefin, PdCk, CO and a secondary amine, have also been reported to undergo carbonylation in the presence of piperidine to afford keto amides (Scheme 9) [51]. 

Water-soluble l,3-bis(di(hydroxyalkyl)phosphino)propane derivatives were thoroughly studied as components of Pd-catalysts for CO/ethene (or other a-olefins) copolymerization and for the terpolymerization of CO and ethene with various a-olefins in aqueous solution (Scheme 7.17) [59], The ligands with long hydroxyalkyl chains consistently gave catalysts with higher activity than sulfonated DPPP and this was even more expressed in copolymerization of CO with a-olefins other than ethene (e.g. propene or 1-hexene). Addition of anionic surfactants, such as dodecyl sulfate (potassium salt) resulted in about doubling the productivity of the CO/ethene copolymerization in a water/methanol (30/2) solvent (1.7 kg vs. 0.9 kg copolymer (g Pd)" h" under conditions of [59]) probably due to the concentration of the cationic Pd-catalyst at the interphase region or around the micelles which solubilize the reactants and products. Unfortunately under such conditions stable emulsions are formed which prevent the re-use... 

Terpolymer blends containing poly(tetrafluoroethylene-co-perfluoro-a-olefins) and platinum nanoparticles imbedded in Nation 1100 fluoropolymer resin were previously prepared by the authors (1) and used as electrodes in fuel cells. 

Radioactive, 4C0 has been used to determine the number of active centers in Ziegler-Natta catalysts for the polymerization of ethylene and a-olefins 31 33>. However, the reliability of this method for active center determination is a matter of discussion 105,106). The argument arises from an uncertainty in the mechanism of the reaction of CO with a metal-polymer bond in the active center. Some model systems have been employed to investigate the mechanism. 

In addition to the familiar and extensive role perfluoroaryl boranes and borates fill as co-catalysts for the coordination polymerization of ethylene and a-olefins, these compounds can act as initiators for other polymerization reactions due to their high Lewis acidity. 

Similarly, the same catalysts that promote the syndiospecific polymerisation of styrene also polymerise ethylene and a-olefins [106,107], ring-substituted styrenes [6] and conjugated dienes [44,74,108-110], These monomers can also be copolymerised with each other [111-114], Substituted styrenes, which yield syndiotactic polymers by polymerisation run with syndiospecific catalysts, form copolymers with styrene the polymerisation rate increases with increasing nucleophilicity of the comonomer. The random copolymers formed are co-syndiotactic [6,111,112]. 

Synthesis. Synthesis of the copolymers was performed by a hydrosilylation reaction of poly(dimethylsiloxane-co-methylhydrosiloxane) (Petrarch System, Inc.) and a-olefins of various lengths (Aldrich). A round-bottomed flask equipped with a magnetic stirring bar, condenser, and calcium chloride tube was charged with a 50% solution of the reactants (up to 10% molar excess of a-olefin) in dry toluene. A solution of hydrogen hexachloroplatinate(IV) in diglyme-isopropyl alcohol (150 ppm Pt) was then added to the reaction mixture. The reaction mixture was stirred at 60 °C for 3 h. At the end of this period, the mixture was refluxed with activated charcoal for 1 h and filtered while hot. Finally the solvent and excess a-olefins were removed under reduced pressure (67 Pa at 100 °C). The reaction proceeded to completion as evidenced by the absence of the Si-H absorption at 2130 cm" in the IR spectra. Residual a-olefin in the purified polymers was determined by gas-liquid chromatography. In all polymers, residual a-olefin was less than 1.5 wt %. 

From the preceding discussions, the salient features of the sulfur atom—olefin systems may be summarized as follows (a) triplet state atoms react with olefins to produce only episulfide in an almost completely stereospecific process, and (f>) the interaction of singlet state sulfur atoms with olefins produces mercaptans, and probably episulfides as well. The kinetics of the reaction is not in accord with the simple mechanism which includes one or more product-forming steps with the olefin molecule in competition with the abstraction reaction from COS, even if allowances are made for collisional relaxation of S( Z)) atoms by COS and the olefin. For this reason, the possibility should be kept in... 

The various reactions of excited carbonyl compounds with olefins may be rationalized on the basis of correlation diagrams. In principle, four different pathways have to be discussed the perpendicular and the parallel approaches (Figure 7.36) and the initial formation of a CO and a CC bond, yielding a C,C-biradical and C,0-biradical, respectively ... 

In Table 1, the C,-C selectivities are listed including the separate values for n-paraffins and a-olefins. The corresponding values for the atmospheric experiments (SSITKA-apparatus) are shown in Table 2. It should be noted that the CO-conversion varies in the range from 10% to 20% for the high pressure experiments, and from 5% to 15% for the atmospheric experiments. However, for each pair of experiments the variation in conversion is small. The trend in the o/n-ratio is clear water treatment before reaction or under reaction decreases the olefin to paraffin ratio. 

Carbonyl complexes of rhodium, ruthenium, osmium, iridium, and platinum, in the presence of H2O and a weak base (e.g., trimethylamine), act as catalysts for the conversion of propene to a mixture of butanol and methylpropanal with the exception of the platinum system, these catalysts are considerably more active than Fe(CO)s as reported by Reppe. Under the same conditions, but in the absence of olefin, the carbonyls act as catalysts for the conversion of CO and H2O to CO2 and H2. The metal carbonyls, together with Fe(CO)s, in the presence of H2O, CO, and a weak base such as McsN, serve as catalysts for the conversion of nitrobenzene, dinitrobenzene, and 2,4- and 2,6-di-nitrotoluene to the corresponding aminobenzene derivatives. 

A variety of co-halo-a-olefin homo- and copolymers have been prepared with Ziegler catalysts. Clark and Powell prepared homopolymers of 4-iodo-l-butene,... 

Brookhart and co-workers recently reported tantalizing results that were close to constituting true copolymerizations of ethylene and methyl acrylate. ° ° The catalyst employed was the palladium version of the diimine complexes that were previously reported for ethylene and a-olefin homopolymerizations (complexes IV). °° The close qualification... 

The co-polymerization of polar monomers other than CO with a-olefins is a field under development and theoretical calculations are just emerging [30,49]. We shall here just review some of the findings of a recent study on the co-polymerization of acrylate with ethylene [30]. 

The insertion of olefins into metal-alkyl linkages is the cornerstone of the preparation of polyolefins and a-olefins, and the insertions of olefins into metal-aryl bonds is one step of a common class of palladium-catalyzed coupling reactions (the Mizoroki-Heck reaction). The insertions of olefins into early-metal-alkyl bonds is part of the so-called Cos-see mechanism of Ziegler-Natta olefin polymerization and of Cramer s mechanism for olefin dimerization. The following sections present examples of these insertion reactions and information on the mechanisms of this type of C-C bond formation. 

The insertion of ethylene and a-olefins into acyl groups is one step of the remarkably selective copolymerization of alkenes and CO to form an alternating copolymer. This process was developed at Shell Chemicals and is discussed in Chapter 17. As depicted in Scheme 9.10, the relative rates for insertion of an alkene into an alkyl group and an acyl group are one factor that controls the selectivity. For high selectivity, the insertion of ethylene into the acyl group must be faster than insertion of ethylene into an alkyl group. ... 

Typical ligands for the organometallic compounds of the transition metals in low oxidation states are CO and the olefins. Therefore, no experiment has been left undone to synthesize such carbonyl or olefin complexes of the elements of the third subgroup and of the lanthanoides. Whereas lanthanoide carbonyls could be detected only in a matrix until now (213), the first indications have been obtained for the existence of olefin complexes. 

Recently, Baird and co-workers have reported (75) examples of polymerizations by a simple mono-Cp titanium complex, (C5(CH3)5)Ti(CH3)3 activated with a Lewis acid (B(C6F5)3) that not only copolymerizes ethylene and a-olefins but also induces polymerization of monomers normally associated with cationic polymerization such as isobutylene and vinyl ethers. Shaffer and Ashbaugh foimd (76) that for isobutylene and a-methylstyrene, the metal complex is an initiator rather than a catalyst (if it even participates at all), but that a transition from cationic to coordination polymerization occurs in styrene polymerization as temperature is raised. Even if it merely functions as an initiator, however, these investigations have revealed new polymerization systems based on anions such as [RB(C6F5)3l (R = alkyl, CeFs) that are less prone to side reactions tending to limit the MW and degree of polymerization of monomers like isobutylene at moderate temperatures (T > -80°C). 

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