Palladium catalyzed ethylene-carbon monoxide alternating copolymerization

A new [(PPh₂CH₂CH₂CH₂PPh₂)Pd(CH₃CN)₂](BF₄)₂/CH₃OH catalyst for olefin/carbon monoxide alternating copolymerization has been found which is far more active and more stable than previous monodente phosphine Pd catalysts. Methanol is a coinitiator as well as a chain transfer agent. Protonic acid is not a coinitiator but causes chain transfers. In the absence of methanol, the copolymerization was characterized by long induction period and slow rate © 1992 John Wiley & Sons, Inc.     

Rare‐earth‐catalyzed alternating copolymerization of carbon monoxide with styrene

Rare‐earth acetates were used to catalyze the copolymerization reaction of carbon monoxide and styrene. Cupric acetate, 1,10‐phenanthroline, p‐toluenesulfonic acid, and 1,4‐benzoquinone were also added to the catalyst system. The structures of the copolymers obtained were characterized with IR, ¹H NMR, ¹³C NMR, wide‐angle X‐ray diffraction, and elemental analysis methods. The relationship between the catalytic activity and the catalyst composition was studied in detail. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 642–649, 2002; DOI 10.1002/pola.10147     

Mechanistic aspects of the metal catalyzed alternating copolymerization of epoxides and carbon monoxide

The cobalt-catalyzed alternating copolymerization of epoxides and CO is a novel, direct approach to aliphatic polyesters, such as poly(hydroxybutyrate) (PHB). This reaction was found to be catalyzed by Ph3Si[Co(CO)4] (4) and pyridine affording in a first step the stable mono-insertion product Ph3Si-O-CH(CH3)-CH2-CO-Co(CO)4 (5). However, a profound mechanistic understanding, especially of the role of pyridine as the key component for the polymerization reaction was missing. ATR-IR online monitoring under catalytic conditions and DFT calculations were used to show that an acylpyridinium cation is formed by cleavage of the cobalt-acyl bond of 5 in the presence of pyridine. The Lewis acid thus generated activates the next incoming epoxide monomer for ring opening through [Co(CO)4]-. The catalytic cycle is completed by a subsequent CO insertion in the new cobalt-alkyl bond. The calculations are used to explore the energetic hypersurface of the polymerization reaction and are complemented by extended experimental investigations that also support the mechanistic hypotheses.     

Enantioselective,alternating copolymerization of carbon monoxide and olefins

Enantioselective, alternating copolymerizations of carbon monoxide with styrene, dicyclopentadiene, and methylcyclopentadiene dimer were carried out with a palladium catalyst modified by 1,4‐3,6‐dianhydro‐2,5‐dideoxy‐2,5‐bis(diphenyl phosphino)‐L ‐iditol. Chiral diphosphine was proven to be effective at enantioselective copolymerization. In the copolymers, some of the second double bonds of alternating poly(1,4‐ketone) were carbonylated. Optical rotation, elemental analysis, and spectra of ¹H NMR, ¹³C NMR, and IR showed that the copolymers had isotactic, alternating poly(1,4‐ketone) structures. An oxidant and an organic acid were the promoters of the copolymerization. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2919–2924, 2000     

Regioselective and stereoselective alternating copolymerization of carbon monoxide with functional olefins

Enantioselective, alternating copolymerizations of carbon monoxide with ω‐undecylenic acid, ethyl acrylate, and butyl acrylate were carried out for the first time with a palladium catalyst modified by 1,4:3,6‐dianhydro‐2,5‐dideoxy‐2,5‐bis(diphenylphosphino)‐L ‐iditol. Optical rotation, elemental analysis, and ¹H NMR,¹³C NMR, and IR spectra showed that the copolymers were optically active, isotactic, alternating poly(1,4‐ketone) or poly(spiroketal) structures. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2027–2036, 2001     

Regio- and stereocontrol in the alternating copolymerization of olefins with carbon monoxide

Strictly alternating copolymers between olefins and carbon monoxide are synthesized using cationic palladium catalysts modified by phosphorus or nitrogen ligands. Basic chelate diphosphines as the ligand allow the regioregular copolymerization of aliphatic olefins thus affording, e.g. in the case of propene, poly(1-oxo-2-methyltrimethylene). Steric control of the copolymerization process towards the production of overwhelmingly isotactic copolymers is possible particularly when using atropisomeric ligands. In the case of styrene as the substrate and for all ligands employed the copolymerization process is regioregular. Prevailing syndiotactic structure is obtained with 1,10-phenanthroline or 2,2′-bipyridine as the ligand. Chelate thioether ligands allow the preparation of a completely atactic material. For 4-tert-butylstyrene an isotactic structure became accessible by using chiral bisoxazolidines. The prevailing structure of the copolymers of cyclopentene corresponds to a 1,3-enchainment of the olefin units most probably associated with a prevailing diisotactic structure     

Anionic alternating copolymerization of epoxide and six‐membered lactone bearing naphthyl moiety

This article describes the anionic copolymerization of glycidyl phenyl ether (GPE) and 1,2‐dihydro‐3H‐naphtho[2,1‐b]pyran‐3‐one (DHNP), a six‐membered aromatic lactone bearing naphthyl moiety. The copolymerization proceeded in a 1:1 alternating manner, to afford the corresponding polyester. The ester linkage in the main chain was cleavable by reduction with lithium aluminum hydride to give the corresponding diol that inherited the structure of the alternating sequence. The copolymerization ability of DHNP permitted its addition as a comonomer to an imidazole‐initiated polymerization of bisphenol A diglycidyl ether. The resulting networked polymer, of which main chain was endowed with the DHNP‐derived rigid naphthalene moieties, showed a higher glass transition temperature than that obtained similarly with using 3,4‐dihydrocoumarin (DHCM) as a comonomer, an analogous aromatic lactone bearing phenylene moiety instead of naphthalene moiety of DHNP. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Enzyme‐Catalyzed Ring‐Opening Polymerization of Unsubstituted β‐Lactam

The synthesis of poly(β‐alanine) by Candida antarctica lipase B immobilized as novozyme 435 catalyzed ring‐opening of 2‐azetidinone is reported. After removal of cyclic side products and low molecular weight species pure linear poly(β‐alanine) is obtained. The formation of the polymer is confirmed with ¹H NMR spectroscopy and MALDI‐TOF mass spectrometry. The average degree of polymerization of the obtained polymer is limited to = 8 by its solubility in the reaction medium. Control experiments with β‐alanine as a substrate confirmed that the ring structure of the 2‐azetidinone is necessary to obtain the polymer.

     

A DFT investigation of the mechanism for alternating copolymerization of styrene with carbon monoxide catalyzed by Pd(II) complexes

Density functional theory has been employed to study the homogeneous catalytic copolymerization of styrene with carbon monoxide.The copolymerization reaction is catalyzed by Pd（Ⅱ） coordinated with 2,2’-bipyridine,a conventional nitrogen-containing bidentate ligand with achiral C_2vsymmetry.The chain propagation mechanism for the alternating copolymerization as well as the side reactions,including multiple insertions of CO and homopolymerization of styrene,has been investigated.This study focused exclusively on regioisomerism and stereoisomerism.We have demonstrated that the strictly alternating copolymerization is kinetically and thermodynamically favored over the side reactions（i.e.,multiple insertions of CO and homopolymerization of styrene）.The regiochemistry study indicates the 2,1 type.Furthermore,the stereochemistry study shows that the syndiotactic conformation is preferred over the isotactic or atactic conformations.     

Synthesis of linear and branched polyketones from the Rh complex catalyzed living alternating copolymerization of (4‐alkylphenyl)allene with CO

Copolymerization of (4‐hexylphenyl)allene and of (4‐dodecylphenyl)allene with carbon monoxide (1 atm) catalyzed by Rh[η³‐CH(Ar′)C{C(CHAr′)CH₂C (CHAr′)CH₂CH₂CHCHAr′}CH₂](PPh₃)₂ (A; Ar′ = C₆H₄OMe‐p) gives the corresponding polyketones: I‐[—CO—C(CHAr)—CH₂—]_n [1: Ar = C₆H₄C₆H₁₃‐p, 2 : Ar = C₆H₄C₁₂H₂₅‐p; I = CH₂C(CHAr′)C(CHAr′)CH₂C(CHAr′)CH₂CH₂CHCHAr′]. Molecular weights of the polyketone prepared from (4‐hexylphenyl)allene and CO are similar to the calculated from the monomer to initiator ratios until the molecular weight reaches to 45,000, indicating the living polymerization. Melting points of the polyketones I‐[—CO—C(CHC₆H₄R‐p)—CH₂—]_n (n = ca. 100) increase in the order R = C₁₂H₂₅ < C₆H₁₃ < C₄H₉ < CH₃ < H. Block and random copolymerization of phenylallene and (4‐alkylphenyl)allene with carbon monoxide gives the new copoly‐ ketones. The polymerization of a mixture of (4‐methylphenyl)allene and smaller amounts of bis(allenyl)benzene under CO afforded the polyketone with a crosslinked structure. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1505–1511, 2000     

Enantioselective isotactic alternating copolymerization of styrene and 4-methylstyrene with carbon monoxide catalyzed by a cationic bioxazoline pd(II) complex

The cationic bioxazoline Pd(II) complex 2 catalyzes the alternating copolymerization of carbon monoxide with styrene and 4-methylstyrene, respectively, to yield a highly isotactic optically active polymer at room temperature and low carbon monoxide pressure (1–4 atm).     

Ruthenium phosphine complexes as catalysts of alternating copolymerization of ethylene and carbon monoxide

The properties of the ruthenium (II) phosphine complexes [Ru(dppe)₂(OTs)₂] and [Ru{PhP(CH₂CH₂CH₂PPh₂)₂}(OTs)₂] as catalysts of alternating copolymerization of ethylene and carbon monoxide were studied. The catalytic activity of these complexes in the absence of cocatalysis is low, but it is substantially increased in the presence of trifluoroacetic acid or 1,4-benzoquinone. These compounds are the first ruthenium complexes which catalyze copolymerization of ethylene and CO. Translated fromAkademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1119–1121, June, 2000.     

Predominant 1,2-insertion of styrene in the Pd-catalyzed alternating copolymerization with carbon monoxide.

The regioselectivity of styrene insertion to an acyl-Pd bond was studied by NMR in (i) a stoichiomeric reaction and (ii) a copolymerization with CO. In the stoichiometric reaction of styrene with [(CH(3)CO)Pd(CH(3)CN)[(R,S)-BINAPHOS]].[B[3,5-(CF(3))(2)C(6)H(3)](4)], both 1,2- and 2,1-products were given. To mimic the real polymerization conditions, a polyketone-substituted complex [[CH(3)(CH(2)CHCH(3)CO)(n)]Pd[(R,S)-BINAPHOS]].[B(3,5-(CF(3))(2)C(6)H(3))(4)] (n approximately 14) was prepared. When this polymer-attached Pd species was treated with styrene, the 1,2-insertion product was the only detectable species. Thus, exclusive 1,2-insertion is demonstrated to be responsible for the styrene-CO copolymerization, in sharp contrast to the predominant 2,1-insertion with conventional nitrogen ligands. Chain-end analysis revealed that beta-hydride elimination took place from the 2,1-complex but not from the 1,2-complex. Thus, once 2,1-insertion occurs, rapid beta-hydride elimination proceeds to terminate the polymerization, as is common to the other phosphorus-ligand systems. The resulting Pd-H species re-initiates the copolymerization, as was proven by MALDI-TOF mass analysis of the product copolymers.     

Asymmetric,regio‐ and stereo‐selective alternating copolymerization of CO2 and propylene oxide catalyzed by chiral chromium Salan complexes

Chiral chromium complexes of tetradentate N,N′‐disubstituted bis(aminophenoxide) (designated as Salan, a saturated version of Schiff‐base Salen ligand) in conjunction with an ionic quaternary ammonium salt can efficiently catalyze the copolymerization of CO₂ with racemic propylene oxide (rac‐PO) at mild conditions to selectively afford completely alternating poly(propylene carbonate) (PPC) with ～ 95% head‐to‐tail linkages and moderate enantioselectivity. These new catalyst systems predominantly exceed the previously much‐studied SalenCr(III) systems in catalytic activity, polymer enantioselectivity, and stereochemistry control. The chiral diamine backbone, sterically hindered substitute groups on the aromatic rings, and the presence of sp³‐hydridized amino donors and its N,N′‐disubstituted groups in chiral SalanCr(III) complexes all play significant roles in controlling polymer stereochemistry and enantioselectivity. Furthermore, a relationship between polycarbonate enantioselectivity and its head‐to‐tail linkages in relation to regioselective ring‐opening of the epoxide was also discussed on the basis of stereochemical studies of PPCs derived from the copolymerization of CO₂ with chiral PO at various conditions. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6102–6113, 2008     

A convenient and practical heterogeneous palladium‐catalyzed carbonylative Suzuki coupling of aryl iodides with formic acid as carbon monoxide source

A practical heterogeneous palladium‐catalyzed carbonylative Suzuki coupling of aryl iodides with arylboronic acids under carbon monoxide gas‐free conditions has been developed using a bidentate phosphino‐functionalized magnetic nanoparticle‐immobilized palladium(II) complex as catalyst. Formic acid was utilized as the carbon monoxide source with dicyclohexylcarbodiimide as the activator, and a wide variety of biaryl ketones were generated in moderate to high yields. The new heterogeneous palladium catalyst can be prepared via a simple procedure and can easily be separated from a reaction mixture by simply applying an external magnet and recycled up to 10 times without any loss of activity.     

Alternating copolymerization of fluoroalkenes with carbon monoxide

The palladium-catalyzed alternating copolymerization of fluoroalkenes, represented as CH(2)=CH-CH(2)-C(n)F(2n+1), with CO was performed using (R,S)-BINAPHOS (2e) as a ligand. The CH(2)-C(n)F(2n+1) group is the most electronegative substituent ever reported for the copolymerization (Taft's sigma value of 0.90 for CH(2)CF(3)). The copolymer obtained from CH(2)=CH-CH(2)-C(8)F(17) (1a) existed as a mixture of polyspiroketal and polyketone, while that from CH(2)=CH-CH(2)-C(4)F(9) (1b) was a pure polyspiroketal, as was revealed by infrared and (13)C-CP/MAS NMR spectroscopies. The terminal structure of the polymer from 1b was confirmed by MALDI-TOF MS spectrometry. Detailed NMR studies suggested that the much higher reactivity with (R,S)-BINAPHOS (2e) than that with the conventional ligand DPPP (2a) can be attributed to the unique 1,2-insertion of the fluoroalkene into acylpalladium species. The existence of an electronegative substituent on the alpha-carbon of the palladium center is successfully avoided in the 1,2-insertion mechanism.     

Preparation,characterization and copolymerization of the 12‐membered cyclic diamide 1,6‐diazacyclododecane‐2,5‐dione

A 12‐membered cyclic diamide monomer for nylon 64 was successfully synthesized in fairly high yield (～45%). The synthesis conditions were varied to see the effect of the diamine and succinyl chloride reactants on yield. Threefold excess of 1,6‐hexamethylenediamine (HDA) gave the highest yield, while further increasing the amount of HDA decreased the yield. Using N,N‐diisopropylethylamine as acid scavenger resulted in the formation of two different cyclic amides, which were fully analyzed by ¹H and ¹³C solution nuclear magnetic resonance spectrometry and mass spectrometry. Copolymerization of cyclic amides with ε‐caprolactam via an anionic route gave a block copolyamide with a two distinct endotherms in the differential scanning calorimetry analysis. However, copolymerization by the hydrolytic route gave only nylon 6 with terminal 64 units. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 96–103     

Nitroxide‐mediated free‐radical copolymerization of styrene with butyl acrylate

Controlled free‐radical copolymerization of styrene (S) and butyl acrylate (BA) was achieved by using a second‐generation nitroxide, N‐tert‐butyl‐N‐[1‐diethylphosphono‐(2,2‐dimethylpropyl)] nitroxide (DEPN), and 2,2‐azobisisobutyronitrile (AIBN) at 120 °C. The time‐conversion first‐order plot was linear, and the number‐average molecular weight increased in direct proportion to the ratio of monomer conversion to the initial concentration, providing copolymers with low polydispersity. The monomer reactivity ratios obtained were r_S = 0.74 and r_BA = 0.29, respectively. To analyze the convenience of applying the Mayo–Lewis terminal model, the cumulative copolymer composition against conversion and the individual conversion of each monomer as a function of copolymerization time were studied. The theoretical values of the propagating radical concentration ratio were also examined to investigate the copolymerization rate behavior. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4168–4176, 2004