Palladium-catalyzed copolymerization

Drent, E. van Broekhoven, J. A. M. Doyle, M. J. Wong, P. K. Palladium Catalyzed Copolymerization of Carbon Monoxide with Alkenes to Alternating Polyketones and Polyspiroketals. Fink, G. Muelhaupt, R. Brintzinger, H. H. Eds. Ziegler Catal. Springer, Berlin, 1995, pp 481 496. 

Koide, Y., Bott, S. G. and Barron, A. R., Alumoxanes as Cocatalysts in the Palladium-catalyzed Copolymerization of Carbon Monoxide and Ethylene Genesis of a Structure-Activity Relationship , Organometallics, 15, 2213-2226 (1996). 

Mecking S, Johnson LK, Wang L, Brookhart M, Mechanistic Studies of the Palladium-Catalyzed Copolymerization of Ethylene and -Olefins with Methyl Acrylate, J Am Chem Soc, 120, 888-899 (1998)... 

A palladium-catalyzed copolymerization of the iridium complex 54 (R = CgHn), containing a dibromo-functionalized acac ligand, with 55 affords phosphorescent copolymers of stoichiometry 56 . 

Koide, Y. Bott, S.G. Barron, A.R. Alumoxanes as cocatalysts in the palladium-catalyzed copolymerization of carbon monoxide and ethylene genesis... 

Fig. 4.J6 Ligands used in the palladium-catalyzed copolymerization of ethylene with norbornenes.

Palladium-catalyzed copolymerization of alkenes with carbon monoxide leading to polyke-tones46 48 represents another example of dicarborative addition. With terminal or other unsymmetrically substituted prostereogenic alkenes a polymer with stereogenic centers along the polymer backbone is generated. 

The first palladium-catalyzed copolymerization of carbon monoxide (CO) with olefins was described in 1982 [11], and as a consequence, carbonylative coupling reactions with alkenes were reported soon after. Notably, it was Negishi and Miller who discovered the first two examples of intramolecular carbonylative Heck reactions of 1-iodopenta-1,4-dienes by applying stoichiometric amounts of palladium [12]. 5-Methylenecyclopent-2-enones as the products were produced in moderate yields (Scheme 7.1). 

Mecking, S., Johnson, L.K., Wang, L. and Brookhart, M. (1998) Mechanistic studies of the palladium-catalyzed copolymerization of ethylene and alpha-olefins with methyl acrylate. Journal of the American Chemical Society 120,888-899. 

Interestingly, the palladium-catalyzed copolymerization of propene and CO may yield a polyspiroketal product, which can be converted into a polyketone (PK-P) by heating or dissolution (69,70). This conversion is reversible (eq. 3). In the presence of an acid the polyspiroketal structure can be (partly) restored (4,54). Also copol5uners of higher a-olefins tend to adopt the polyspiroketal form (4). 

Batistini, A. Consiglio, G Suter, U. W. Regioselectivity control in the palladium-catalyzed copolymerization of propylene with carbon monoxide. Angew. Chem., Int. Ed. Engl. 1992, 31, 303-305. 

Gambs, C. Chaloupka, S. Consigho, G Togni, A. Ligand electronic effect in enantioselective palladium-catalyzed copolymerization of carbon monoxide and propene. Angew. Chem., Int. Ed. 2000, 39, 2486-2488. 

ILs provide a useful medium for the palladium-catalyzed copolymerization of styrene and carbon monoxide [96]. The catalytic system exhibits excellent polyketone productivity (up to 24 kg of polymer g Pd) with a low palladium loading (styrene/ Pd =100000) at 40 bar CO. Besides the enhanced productivity over conventional solvents, IL catalytic solutions show no drop in yields and polydispersity after at least four successive recycles. 

PALLADIUM-CATALYZED ALTERNATING COPOLYMERIZATION OF ALKENES AND CARBON MONOXIDE... 

Polymers containing chromophores such as acridine and azobenzene have also been prepared by palladium-catalyzed amination according to two approaches [222-224]. The first approach involved the polymerization of monomers containing the chromophore. For example, 4-aminoazobenzene was condensed with 1,3-dibromobenzene (Eq. (39)) or 4,4 -dibromobiphenyl ether to form polymeric materials with Mw values of 9.0 x 103 and 19 x 103, respectively. Alternatively, polymers prepared by polymerization of 4-bromostyrene or copolymerization of styrene and 4-bromostyrene were coupled with N-phenyl-4-amino azobenzene. Substitution of the aryl bromides by the amino azobenzene unit was essentially quantitative when using P(tBu)3 as the ligand. 

It is interesting to draw a parallel between the palladium-catalyzed homogeneous olefin/CO copolymerization and the modem homogeneous olefin polymerization catalyzed by early transition metal complexes [39] (Table 1), which allows the following similarities to be noted. 

Using a related reaction. Sen showed that the palladium-catalyzed alternating copolymerization of CO and olefins could be carried out under aqueous conditions by using either the sulfonated chelating phosphine ligand, l,3-bis(diphenyl-phosphino)propane (dppp), or a sulfonated phenanthroline ligand, Phen-SO. Na (eq. (9)) [32]. 

Carbon monoxide insertions into palladium-alkyl or palladium-aryl bonds were extensively studied in connection with the palladium-catalyzed CO-olefin copolymerization process . 

Ditertiary phosphines such as (86), (92), and (98) (100) (Scheme 6) have found important uses as ligands for metal-catalyzed transformations, including e.g., palladium-catalyzed Grignard cross couplings,194,205 rhodium-catalyzed Michael additions,2 hydrocyanations,206 copolymerizations,20 and palladium-catalyzed animations.208 Rhodium complexes of (86) are catalysts for the carbonylation of methanol.188 More recently the ligand bite angle of ditertiary phosphines such as (100) has been shown to influence catalytic activity/selectivity in several important catalytic processes.209-213... 

Scheme 8.6 Various chelate di-phosphorus ligands used for palladium-catalyzed carbon monox-ide-ethene copolymerization.

E Drent, PHM Budzelaar. Palladium-Catalyzed Alternating Copolymerization of Al-kenes and Carbon Monoxide. Chem Rev 96 663-681, 1996. 

Subjects specifically excluded are cycloolefin polymerizations catalyzed by naked nickel catalysts, palladium-catalyzed ethylene/carbon monoxide alternating copolymerizations, metathesis polymerizations of cyclic olefins, and diene polymerizations... 

Polyketones formed by the palladium-catalyzed alternating copolymerization of styrene and CO have become the subject of a great deal of attention [43]. Almost concurrently, two papers appeared describing this reaction in ionic liquids [44,45]. Seddon et al. used [Pd(bipy)2][PFs] in a variety ofionic liquids (Scheme 7-1) [44]. The complex was active in methanol [ca. 17.4 kg (g Pd) ], but the product polyketone was contaminated with palladium. In the ionic liquids the activity of the catalyst was dependent on the nature of the anion, decreasing in the order [N(S02CFj)2]"... 

Swager and coworkers synthesized receptor polymers 102 and 103 [209,210]. The polymers were prepared by copolymerization of 2,5-dibromo-3-decylthiophene or 3,3 -bis(methoxyethoxy)-2,2 -bithiophene with the organozinc derivative of the macrocyclic 3,3 -dialkoxy-2,2 -bithiophene by palladium-catalyzed cross-coupling. Cyclic voltammetry and in situ conductivity measurements on polymer films have evidenced the complexation of paraquat derivatives. However, the complexation between polymer films and acceptors can lead to opposite shifts of oxidation potential of the polymer due to the interplay of donor-acceptor interaction and conformational changes of the polymer. 

More recently, the alternating copolymerization of vinyl acetate with carbon monoxide via a palladium catalyzed coordination insertion mechanism has been reported. This is the first report of a nonradical pathway for vinyl acetate polymerization. 

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