Special Issue "Molecular Catalysis for Precise Olefin Polymerization and ROP 2015"

A special issue of Catalysts (ISSN 2073-4344).

Deadline for manuscript submissions: closed (15 January 2016)

Special Issue Editor

Guest Editor
Prof. Dr. Carl Redshaw

School of Mathematics & Physical Sciences, University of Hull, Hull, UK
Website | E-Mail
Interests: calixarenes; coordination chemistry’ catalysis; polymers; imaging and anti-cancer agents

Special Issue Information

Dear Colleagues,

The growth of emerging markets, particularly in the Far East, has fuelled the demand for new plastic materials. This in turn has stimulated both academic and industrial interest in the design of catalyst systems for which new Intellectual Property (IP) can be generated, and in new polymeric materials possessing desirable properties such as biodegradability.

Underpinning much of the work is synthetic chemistry and, in particular, ligand design. The ability to tune the electronic and steric properties of the resultant metal catalysts and thereby influence both the catalytic activity, as well as the resultant polymer properties, is proving particularly fruitful. Traditionally, early transition metals have been employed particularly for polyolefin synthesis, but in recent years late transition metals have emerged as intruging alternatives. For ring opening polymerization systems, catalysts incorporating elements from many parts of the periodic table are showing promise.

In this Special Issue, we would like to highlight manuscripts focusing on aspects of new catalysts systems for the homo- or co-polymerization of alpha-olefins, the ring opening of lactides and/or lactones and on any mechanistic/spectroscopic aspects that give insight into such systems. This Special Issue aims to cover recent progress in the area and should provide a nice collection of papers that will be of immense interest to those involved in catalyst design, organometallic chemistry and polymer synthesis.

Prof. Dr. Carl Redshaw
Guest Editor

Manuscript Submission Information

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Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1000 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • catalyst design
  • polymerization catalysis
  • ring opening polymerization
  • polymers
  • oligomers
  • biodegradable
  • transition metals
  • synthesis
  • characterization
  • mechanistics

Published Papers (7 papers)

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Editorial

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Open AccessEditorial Molecular Catalysis for Precise Olefin Polymerization and ROP 2015
Catalysts 2016, 6(4), 53; doi:10.3390/catal6040053
Received: 24 March 2016 / Accepted: 30 March 2016 / Published: 31 March 2016
PDF Full-text (159 KB) | HTML Full-text | XML Full-text
Abstract
The growth of emerging markets, particularly in the Far East, has fuelled the demand for new plastic materials.[...] Full article
(This article belongs to the Special Issue Molecular Catalysis for Precise Olefin Polymerization and ROP 2015)

Research

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Open AccessArticle Homo-Polymerization of 1-Hexene Catalysed by O^N^N (Salicylaldimine)Iron(III) Pre-Catalysts to Branched Poly(1-hexene)
Catalysts 2016, 6(3), 47; doi:10.3390/catal6030047
Received: 22 September 2015 / Revised: 1 March 2016 / Accepted: 2 March 2016 / Published: 17 March 2016
Cited by 1 | PDF Full-text (1152 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Five new iron(III) 1-hexene polymerisation catalysts were prepared from the reactions of 2,4-di-tert-butyl-6-(2-(1H-imidazol-4-yl)ethylimino)methylphenol (L1), or 4-tert-butyl-6-(2-(1H-imidazol-4-yl)ethylimino)methylphenol (L2) or 2,4-di-tert-butyl-6-[(2-pyridin-2-yl-ethylimino)-methyl-phenol (L3) with anhydrous iron(II) halides to form [FeCl2(L1)] (1), [FeBr2(L1)] (2), [FeI2(L1)]
[...] Read more.
Five new iron(III) 1-hexene polymerisation catalysts were prepared from the reactions of 2,4-di-tert-butyl-6-(2-(1H-imidazol-4-yl)ethylimino)methylphenol (L1), or 4-tert-butyl-6-(2-(1H-imidazol-4-yl)ethylimino)methylphenol (L2) or 2,4-di-tert-butyl-6-[(2-pyridin-2-yl-ethylimino)-methyl-phenol (L3) with anhydrous iron(II) halides to form [FeCl2(L1)] (1), [FeBr2(L1)] (2), [FeI2(L1)] (3), [FeBr2(L2)] (4) and [FeCl2(L3)] (5). All the iron(III) complexes 1–5 were activated with EtAlCl2 to produce active catalysts for the polymerisation of 1-hexene to low molecular weight poly(1-hexene) (Mn = 1021–1084 Da) and very narrow polydispersity indices (1.19–1.24). 1H and 13C{1H} NMR analysis showed the polymers are branched with methyl, butyl and longer chain branches. The longer chain branches are dominant indicating that 2,1-insertion of monomer is favoured over 1,2-insertion in the polymerisation reaction. Full article
(This article belongs to the Special Issue Molecular Catalysis for Precise Olefin Polymerization and ROP 2015)
Open AccessArticle Pyrazole Supported Zinc(II) Benzoates as Catalysts for the Ring Opening Copolymerization of Cyclohexene Oxide and Carbon Dioxide
Catalysts 2016, 6(1), 17; doi:10.3390/catal6010017
Received: 29 September 2015 / Revised: 8 January 2016 / Accepted: 11 January 2016 / Published: 20 January 2016
Cited by 2 | PDF Full-text (2197 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The bis(pyrazole)zinc(II) benzoate complexes bis(3,5-diphenylpyrazole)zinc(II) benzoate (1), bis(3,5-diphenylpyrazole)zinc(II) 3,5-dinitrobenzoate (2), bis(3,5-diphenylpyrazole)zinc(II) 4-hydroxybenzoate (3), and bis(3,5-di-tert-butylpyrazole)zinc(II) 2-chlorobenzoate (4) were synthesized from the reaction of 3,5-diphenylpyrazole (L1) or 3,5-di-tert-butylpyrazole (L2
[...] Read more.
The bis(pyrazole)zinc(II) benzoate complexes bis(3,5-diphenylpyrazole)zinc(II) benzoate (1), bis(3,5-diphenylpyrazole)zinc(II) 3,5-dinitrobenzoate (2), bis(3,5-diphenylpyrazole)zinc(II) 4-hydroxybenzoate (3), and bis(3,5-di-tert-butylpyrazole)zinc(II) 2-chlorobenzoate (4) were synthesized from the reaction of 3,5-diphenylpyrazole (L1) or 3,5-di-tert-butylpyrazole (L2), zinc(II) acetate and the appropriate benzene carboxylic acid. The molecular structure of complex 2 confirmed that these zinc(II) benzoate complexes adopt a 4-coordinate tetrahedral geometry. All four complexes were screened as catalysts for the copolymerization of carbon dioxide (CO2) and cyclohexene oxide (CHO) and were found to be active for the formation of poly(cyclohexene carbonate) (PCHC) at CO2 pressures as low as 1.0 MPa under solvent-free conditions and without the use of a co-catalyst. At some reaction condition, most of the catalysts produced PCHC with high carbonate content of up to 98% and a good amount of cyclic cyclohexene carbonate (CCHC). The copolymers produced have low to moderate molecular weights (5200–12300 g/mol) and with polydispersity indices that vary from 1.19 to 2.50. Matrix Assisted Laser Desorption/Ionization-Time of Flight Mass Spectra (MALDI-TOF MS) of these copolymers showed they have benzoate and hydroxyl end groups. Full article
(This article belongs to the Special Issue Molecular Catalysis for Precise Olefin Polymerization and ROP 2015)
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Open AccessArticle Synthesis of Ethylene or Propylene/1,3-Butadiene Copolymers Possessing Pendant Vinyl Groups with Virtually No Internal Olefins
Catalysts 2015, 5(4), 2001-2017; doi:10.3390/catal5042001
Received: 7 October 2015 / Accepted: 12 November 2015 / Published: 20 November 2015
Cited by 2 | PDF Full-text (620 KB) | HTML Full-text | XML Full-text
Abstract
In general, ethylene/1,3-butadiene copolymerizations provides copolymers possessing both pendant vinyls and vinylenes as olefinic moieties. We, at MCI, studied the substituent effects of C2-symmetric zirconocene complexes, rac-[Me2Si(Indenyl’)2]ZrCl2 (Indenyl’ = generic substituted indenyl), after activation on
[...] Read more.
In general, ethylene/1,3-butadiene copolymerizations provides copolymers possessing both pendant vinyls and vinylenes as olefinic moieties. We, at MCI, studied the substituent effects of C2-symmetric zirconocene complexes, rac-[Me2Si(Indenyl’)2]ZrCl2 (Indenyl’ = generic substituted indenyl), after activation on the ratio of the pendant vinyls and vinylenes of the resultant copolymers. Complexes examined in this study were rac-dimethylsilylbis (1-indenyl)zirconium dichloride (1), rac-dimethylsilyl-bis[1-(2-methyl-4,5-benzoindenyl)] zirconium dichloride (2), rac-dimethylsilyl-bis[l-(2-methyl -4-phenylindenyl)]zirconium dichloride (3), rac-dimethy1si1y1- bis(2-ethyl-4-phenylindenyl) zirconium dichloride (4), rac-dimethylsilyl-bis[l-(2-n-propyl -4-(1-naphthyl)indenyl)]zirconium dichloride (5), rac-dimethylsilyl-[1-(2-ethyl-4-(5-(2,2-dimethyl-2,3-dihydro-1H-cyclopenta [a]naphthalenyl)indenyl))][1-(2-n-propyl-4-(5-(2,2-dimethyl-2,3-dihydro-1H-cyclopenta[a] naphthalenyl)indenyl))]zirconium dichloride (6), rac-dimethylsilyl-bis[1-(2-ethyl-4-(9-phenanthryl)indenyl)]zirconium dichloride (7), and rac-dimethylsilyl-bis[l-(2-n-propyl-4-(9-phenanthryl)indenyl)]zirconium dichloride (8). We found that the ratio of the pendant vinyls and vinylenes is strongly affected by the bulkiness of the substituent on the complexes examined. The vinyl content increased linearly in the following order, 8 > 7 > 6 > 5 > 4 > 3 > 2 > 1. Notably, complex 8/DMAO formed ethylene/1,3-butadiene copolymers possessing predominant vinyl groups, which can be crucial precursors for functionalized polyolefins. Likewise, complex 8/DMAO afforded propylene/1,3-butadiene copolymers with predominant vinyl groups. Full article
(This article belongs to the Special Issue Molecular Catalysis for Precise Olefin Polymerization and ROP 2015)
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Open AccessArticle Molybdenum (VI) Imido Complexes Derived from Chelating Phenols: Synthesis, Characterization and ɛ-Caprolactone ROP Capability
Catalysts 2015, 5(4), 1928-1947; doi:10.3390/catal5041928
Received: 23 September 2015 / Revised: 20 October 2015 / Accepted: 2 November 2015 / Published: 12 November 2015
Cited by 4 | PDF Full-text (604 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Reaction of the bulky bi-phenols 2,2′-RCH[4,6-(t-Bu)2C6H2OH]2 (R = Me L1MeH2, Ph L1PhH2) with the bis(imido) molybdenum(VI) tert-butoxides [Mo(NR1)(NR2)(Ot-Bu)2
[...] Read more.
Reaction of the bulky bi-phenols 2,2′-RCH[4,6-(t-Bu)2C6H2OH]2 (R = Me L1MeH2, Ph L1PhH2) with the bis(imido) molybdenum(VI) tert-butoxides [Mo(NR1)(NR2)(Ot-Bu)2] (R1 = R2 = 2,6-C6H3-i-Pr2; R1 = t-Bu, R2 = C6F5) afforded, following the successive removal of tert-butanol, the complexes [Mo(NC6H3i-Pr2-2,6)2L1Me] (1), [Mo(NC6H3i-Pr2-2,6)2L1Ph] (2) and [Mo(Nt-Bu)(μ-NC6F5)(L1Me)]2 (3). Similar use of the tri-phenol 2,6-bis(3,5-di-tert -butyl-2-hydroxybenzyl)-4-methylphenol (L2H3) with [Mo(NC6H3i-Pr2-2,6)2(Ot-Bu)2] afforded the oxo-bridged product [Mo(NC6H3i-Pr2-2,6)(NCMe)(μ-O)L2H]2 (4), whilst use of the tetra-phenols α,α,α′,α′-tetrakis(3,5-di-tert-butyl-2-hydroxyphenyl)-p- or -m-xylene L3pH4/L3mH4 led to {[Mo(NC6H3i-Pr2-2,6)2]2(μ-L3p)} (5) or {[Mo(NC6H3i-Pr2-2,6)2]2(μ-L3m)} (6), respectively. Similar use of [Mo(NC6F5)2(Ot-Bu)2] with L3pH4 afforded, after work-up, the complex {[Mo(NC6F5)(Ot-Bu)2]2(μ-L3p)}·6MeCN (7·6MeCN). Molecular structures of 1, 2·CH2Cl2, 3, 4·6MeCN, 6·2C6H14, and 7·6MeCN are reported and these complexes have been screened for their ability to ring open polymerize (ROP) ε-caprolactone; for comparative studies the precursor complex [Mo(NC6H3i-Pr2-2,6)2Cl2(DME)] (DME = 1,2-dimethoxyethane) has also been screened. Results revealed that good activity is only achievable at temperatures of ≥100 °C over periods of 1 h or more. Polymer polydispersities were narrow, but observed molecular weights (Mn) were much lower than calculated values. Full article
(This article belongs to the Special Issue Molecular Catalysis for Precise Olefin Polymerization and ROP 2015)
Open AccessArticle Copolymerization of Ethylene and Vinyl Amino Acidic Ester Catalyzed by Titanium and Zirconium Complexes
Catalysts 2015, 5(4), 1831-1845; doi:10.3390/catal5041831
Received: 7 September 2015 / Revised: 14 October 2015 / Accepted: 16 October 2015 / Published: 30 October 2015
Cited by 3 | PDF Full-text (278 KB) | HTML Full-text | XML Full-text
Abstract
A series of titanium and zirconium complexes with ligands based on di-isopropyl phosphorus-phenylamine and their derivatives were synthesized and characterized. These catalysts were utilized to catalyze the copolymerization of ethylene with N-acetyl-O-(dec-9-enyl)-L-tyrosine ethyl ester with high catalytic activity of 6.63
[...] Read more.
A series of titanium and zirconium complexes with ligands based on di-isopropyl phosphorus-phenylamine and their derivatives were synthesized and characterized. These catalysts were utilized to catalyze the copolymerization of ethylene with N-acetyl-O-(dec-9-enyl)-L-tyrosine ethyl ester with high catalytic activity of 6.63 × 104 g P (mol Ti)−1 h−1 after activation by methylaluminoxane (MAO). The effects of ligand structure, metal atoms (Ti, Zr) and polymerization conditions were investigated in detail. The obtained polymers were characterized by 13C-NMR, DSC, FT-IR, and GPC. The results showed that the obtained copolymer had a high comonomer incorporation rate of 2.56 mol % within the copolymer chain. The melting temperature of the copolymer was up to 138.9 °C, higher than that of the obtained homopolyethylene. Full article
(This article belongs to the Special Issue Molecular Catalysis for Precise Olefin Polymerization and ROP 2015)
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Open AccessArticle Dimethyl-Aluminium Complexes Bearing Naphthyl-Substituted Pyridine-Alkylamides as Pro-Initiators for the Efficient ROP of ε-Caprolactone
Catalysts 2015, 5(3), 1425-1444; doi:10.3390/catal5031425
Received: 9 July 2015 / Revised: 27 July 2015 / Accepted: 31 July 2015 / Published: 11 August 2015
Cited by 4 | PDF Full-text (837 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Three sterically-enhanced 2-imino-6-(1-naphthyl)pyridines, 2-{CMe=N(Ar)}-6-(1-C10H7)C5H3N [Ar = 2,6-i-Pr2C6H3 (L1dipp), 2,4,6-i-Pr3C6H2 (L1tripp), 4-Br-2,6-i-Pr2C
[...] Read more.
Three sterically-enhanced 2-imino-6-(1-naphthyl)pyridines, 2-{CMe=N(Ar)}-6-(1-C10H7)C5H3N [Ar = 2,6-i-Pr2C6H3 (L1dipp), 2,4,6-i-Pr3C6H2 (L1tripp), 4-Br-2,6-i-Pr2C6H2 (L1Brdipp)], differing only in the electronic properties of the N-aryl group, have been prepared in high yield by the condensation reaction of 2-{CMe=O}-6-(1-C10H7)C5H3N with the corresponding aniline. Treatment of L1dipp, L1tripp and L1Brdipp with two equivalents of AlMe3 at elevated temperature affords the distorted tetrahedral 2-(amido-prop-2-yl)-6-(1-naphthyl)pyridine aluminum dimethyl complexes, [2-{CMe2N(Ar)}-6-(1-C10H7)C5H3N]AlMe2 [Ar = 2,6-i-Pr2C6H3 (1a), 2,4,6-i-Pr3C6H2 (1b), 4-Br-2,6-i-Pr2C6H2 (1c)], in good yield. The X-ray structures of 1a1c reveal that complexation has resulted in concomitant C–C bond formation via methyl migration from aluminum to the corresponding imino carbon in L1aryl; in solution, the restricted rotation of the pendant naphthyl group in 1 confers inequivalent methyl ligand environments. The ring opening polymerization of ε-caprolactone employing 1, in the presence of benzyl alcohol, proceeded efficiently at 30 °C producing polymers of narrow molecular weight distribution with the catalytic activities dependent on the nature of the substituent located at the 4-position of the N-aryl group with the most electron donating i-Pr derivative exhibiting the highest activity (1b > 1a > 1c); at 50 °C 1b mediates 100% conversion of the monomer to polycaprolactone (poly(CL)) in one hour. In addition to 1a, 1b and 1c, the single crystal X-ray structures are reported for L1dipp and L1tripp. Full article
(This article belongs to the Special Issue Molecular Catalysis for Precise Olefin Polymerization and ROP 2015)
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