Ethene-CO copolymerization

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... 

Figure 7.7 Selected P H NMR spectra recorded during a CO/ethene copolymerization assisted by [Pd TFA)2(Na2DPPPDS)] in the presence of 20 equiv of TsOH and a 1 1 CO/C2H4 pressure of 600 psi (10 mm sapphire tube, D2O, 20—85°C,...

Scheme 8.3 Proposed catalytic cycle for the growing steps of the CO-ethene copolymerization starting with [Pd(dppp)(CH3)(OSO2CF3)] (GPC=growing polymer chain).

Nearly 40 years have evolved between the first discovery by Reppe of transition-metal-catalyzed CO/ethene copolymerization and the discovery in 1983, at Shell, of a class of highly active, high yield palladium catalysts for the synthesis of high molecular weight, perfectly alternating CO/ethene copolymers [PK-E, Fig. 1], This class of catalysts is also active for the co- and terpol5unerization of CO with alkenes other than ethene, both simple aliphatic and heteroatom functionalized, thus providing access to a family of completely new polyketone polymers. 

Table 2. Performance of Selected Catalysts in CO/Ethene Copolymerization ...

Palladium-Catalyzed CO/Ethene Copolymerization 9 Table 1.3 Platinum/tin-catalyzed hydroformylation of 1-octene at E0°C.°... 

Water-soluble dicationic palladium(II) complexes [(R.2P(CH2)3PR.2)Pd-(NCMe)2][BF4]2 proved to be highly active in the carbon monox-ide/ethene copolymerization under biphasic conditions (water-toluene). In the presence of an emulsifier and methanol as activator, the catalytic activity increased by a factor of about three. Also higher olefins could be successfully incorporated into the copolymerization with CO and the terpolymerization with ethene and CO.184... 

The water-soluble palladium complex prepared from [Pd(MeCN)4](Bp4)2 and tetrasulfonated DPPP (34, n=3, m=0) catalyzed the copolymerization of CO and ethene in neutral aqueous solutions with much lower activity [21 g copolymer (g Pd) h ] [53] than the organosoluble analogue in methanol. Addition of strong Brpnsted acids with weakly coordinating anions substantially accelerated the reaction, and with a catalyst obtained from the same ligand and from [Pd(OTs)2(MeCN)2] but in the presence of p-toluenesulfonic acid (TsOH) 4 kg copolymer was produced per g Pd in one hour [54-56] (Scheme 7.16). Other tetrasulfonated diphosphines (34, n=2, 4 or 5, m=0) were also tried in place of the DPPP derivative, but only the sulfonated DPPB (n=4) gave a catalyst with considerably higher activity [56], Albeit with lower productivity, these Pd-complexes also catalyze the CO/ethene/propene terpolymerization. 

A conventional approach to fhe controlled formation of short-chain branches is ethene copolymerization wifh co-monomers such as propene, butene(l), 4-mefhyl-pentene(l), hexene(l) or octene(l). In the ethene/propene copolymerization example given below an increased number of methyl groups compared with vinyl end groups is consistent wifh a propene incorporation of approximately 6 mol% [Eq. (13)], fhe observed lower DSC melt temperatures and lower densities are typical for medium density (MDPE) and hnear low density polyethylene (LLDPE). 

X-1 copolymerizes ethene with Nqh and Nac- In the case of 5-norbomene-2-yl acetate, the activity and molar masses resemble those of E-co-N copolymerization. 

Figure 18 Copolymerization diagram for co(ethene-Un-OH) with different metallocenes. Reproduced from Ahjopalo, L. Lofgren, B. Hakala, K. etal. Eur. Polym. J. 1999, 35,1519. ...

Two competing chain-transfer mechanisms in copolymerization of CO and ethene catalyzed by Pd11 acetate/dppp complexes were found. One involves termination via an isomerization into the enolate followed by protonation with methanol the rate of this reaction should be independent of the concentration of the protic species. The second chain-transfer mechanism comprises termination via methanolysis of the acylpalladium species, and subsequent initiation by insertion of ethene into the palladium hydride bond.501... 

The mechanism for the alternating copolymerization of ethene with CO has been studied both experimentally and theoretically to explain the completely alternating nature of this process. 

The virtually unlimited availability of CO renders it extremely appealing as a monomer in copolymerization reactions. Herrmann and co-workers [21] reported the copolymerization of CO and ethene using dicationic chelating carbene complexes of palladium(II) (Fig. 2). Given the large molecular weight of the obtained copolymer and the relatively modest TONs they observed, the authors postulated that only a small percentage of palladium pre-catalyst actually participates in the production of copolymer. 

In this more interesting case, each monomer adds only to an end unit of the other kind (k = 0, km - 0). In the polymer, units MA and M then alternate. Coordination copolymerization of olefins and carbon monoxide, catalyzed by complex hydrides of Pd(II) or Rh(I) in the presence of an alcohol co-solvent to yield polyketo esters, provides an example [133,134] Olefin and carbon monoxide are added altematingly, and reaction with alcohol terminates the kinetic chain and restores the catalyst. For ethene as the olefin ... 

Mw/M = 2, highly linear Copolymerization random distribution, LLDPE co-monomers propene, 1-butene, 1-octene Elastomers, Terpolymers of Ethene, Propene and Diene low transition metal concentration in the polymer, narrow molecular weight distribution Polymerization to ... 

The copolymerization of ethene and CO produces an interesting polar material with alternating C2 alkane and carbonyl groups. If a monosub-stituted alkene is used, isotactic and syndiotactic polymers can result. The usual catalyst for such a process is a Pd-phosphine complex. If the phosphine ligand is chiral, stereoregularity with reference to the pendant group from the alkene can result. 

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