Invited Review | Published:

Polymer Synthesis and Reactions

Non-bridged half-metallocene complexes of group 4–6 metals with chelating ligands as well-defined catalysts for α-olefin polymerization

Polymer Journal volume 47, pages 217 (2015) | Download Citation

Abstract

Tremendous effort has been directed toward the design of an organic ligand framework around the catalytically active metal center of homogeneous catalyst precursors. This work is aimed at controlling not only the reactivity of the metal catalysts for α-olefin polymerization but also the molecular weight, molecular weight distribution, polymer microstructure and monomer content of the copolymers. Among the catalyst precursor categories, non-bridged half-metallocene complexes supported by a variety of chelating ligands are attractive catalyst motifs for ethylene homopolymerization, ethylene/α-olefin copolymerization and stereoselective polymerization of α-olefins. These motifs are attractive in terms of their rather simple synthetic protocols and the wide range of potential architectural designs of the attached ligands. This review article summarizes recent developments regarding non-bridged half-metallocene complexes of group 4–6 metals with anionic chelating ligands. In contrast to the conventional metallocene initiators Cp2MX2 (Cp=η5-C5H5), half-metallocene complexes of the type CpM(L^L)X2 (L^L=chelating ligands) offer the advantage of catalyst modification. Steric and/or electronic modification of the coordination environment can be achieved by changing one cyclopentadienyl ligand of a metallocene complex to another ligand, such as three-, four-, five-, six- or seven-membered chelates having bidentate or tridentate coordinations and being monoanionic, dianionic or trianionic. Half-metallocene complexes with a four-membered chelating ring are focused on due to their unique dynamic behaviors of metal-centered racemization and chain transfer. The structural uniqueness of the metal complexes, the effects of the chelate ring sizes on their productivity and the activation processes of the metal complexes with cocatalysts are highlighted.

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References

  1. 1.

    (ed.). Frontiers in metal-catalyzed polymerization (special issue). Chem. Rev. 100, 4 (2000).

  2. 2.

    & Ziegler-Natta catalysis. Adv. Organomet. Chem. 18, 99–149 (1980).

  3. 3.

    ., ., & Bis(cyclopentadienyl)zirkon-verbindungen und aluminoxan als Ziegler-Katalysatoren für die polymerisation und copolymerisation von olefinen. Makromol. Chem. Rapid Commun. 4, 417–421 (1983).

  4. 4.

    & Metallocene-Based Polyolefins, (Wiley, 2000).

  5. 5.

    ., ., ., & Stereospecific olefin polymerization with chiral metallocene catalysts. Angew. Chem. Int. Ed. 34, 1143–1170 (1995).

  6. 6.

    ., ., & Late Transition Metal Polymerization Catalysis, (Wiley, 2003).

  7. 7.

    ., & Catalysts for the living insertion polymerization of alkenes: access to new polyolefin architectures using Ziegler-Natta chemistry. Angew. Chem. Int. Ed. 41, 2236–2257 (2002).

  8. 8.

    & Advances in non-metallocene olefin polymerization catalysis. Chem. Rev. 103, 283–315 (2003).

  9. 9.

    ., ., ., & Living alkene polymerization: new methods for the precision synthesis of polyolefins. Prog. Polym. Sci. 32, 30–92 (2007).

  10. 10.

    & Group 4 ansa-cyclopentadienyl-amido catalysts for olefin polymerization. Chem. Rev. 98, 2587–2598 (1998).

  11. 11.

    ., ., & Nonbridged half-metallocenes containing anionic ancillary donor ligands: new promising candidates as catalysts for precise olefin polymerization. J. Mol. Cat. A Chem. 267, 1–29 (2007).

  12. 12.

    ., & Mono-η-cyclopentadienyl-benzamidinato compounds of titanium, zirconium and hafnium. J. Chem. Soc. Chem. Commun. 1415–1417 (1993).

  13. 13.

    ., & Metall-N,N'-bis(trimethylsilyl)benzamidinate: Synthese und Kristallstruktur von Bis[N,N-bis(trimethylsilyl)benzamidinato)chroni(II), [PhC(NSiMe3)2]2Cr. Z. Naturforsch. 46B, 1328–1332 (1991).

  14. 14.

    ., & Unexpected reactions of pentafluorophenylboron compounds with η-cyclopentadienyl(benzamidinato)zirconium derivatives. J. Chem. Soc. Chem. Commun. 2607–2608 (1994).

  15. 15.

    ., ., ., ., & Mono-η-7-cyclopentadienyl-benzamidinato chloro compounds of titanium, zirconium and hafnium. J. Organomet. Chem. 491, 153–158 (1995).

  16. 16.

    ., ., ., ., & Metallocene analogues containing bulky heteroallylic ligands and their use as new olefin polymerization catalysts. J. Mol. Cat. A Chem. 130, 149–162 (1998).

  17. 17.

    ., ., & Synthesis of and ethylene polymerization using iminophosphonamide complexes of group 4. Organometallics 18, 2731–2733 (1999).

  18. 18.

    & Rapid access to dimethylcyclopentadienyltitanium(IV) amidinate, (C5R5)TiMe2[NR1C(R2)NR3] (R=H and Me; R2=Me), libraries. Organometallics 17, 5228–5230 (1998).

  19. 19.

    ., & Stereospecific syntheses, metal configurational stabilities, and conformational analyses of meso-(R,S)- and (R,R)-(η5-C5R5)Ti(CH3)2-N,N’-bis(1-phenylethyl)acetamidinates for R=H and Me. Organometallics 18, 4183–4190 (1999).

  20. 20.

    & Stereospecific living Ziegler−Natta polymerization of 1-hexene. J. Am. Chem. Soc. 122, 958–959 (2000).

  21. 21.

    ., ., ., & Dramatic enhancement of activities for living Ziegler−Natta polymerizations mediated by “exposed” zirconium acetamidinate initiators:  the isospecific living polymerization of vinylcyclohexane. J. Am. Chem. Soc. 123, 6197–6198 (2001).

  22. 22.

    ., ., & Living Ziegler−Natta cyclopolymerization of nonconjugated dienes:  new classes of microphase-separated polyolefin block copolymers via a tandem polymerization/cyclopolymerization strategy. J. Am. Chem. Soc. 122, 10490–10491 (2000).

  23. 23.

    ., ., & Regarding the stability of d0 monocyclopentadienyl zirconium acetamidinate complexes bearing alkyl substituents with β-hydrogens. J. Am. Chem. Soc. 124, 5932–5933 (2002).

  24. 24.

    ., & A case for asymmetric hydrozirconation. J. Am. Chem. Soc. 125, 8746–8747 (2003).

  25. 25.

    ., & Degenerative transfer living Ziegler−Natta polymerization:  application to the synthesis of monomodal stereoblock polyolefins of narrow polydispersity and tunable block length. J. Am. Chem. Soc. 125, 9062–9069 (2003).

  26. 26.

    ., ., & Goldilocks effect of a distal substituent on living Ziegler−Natta polymerization activity and stereoselectivity within a class of zirconium amidinate-based initiators. Organometallics 23, 3512 (2004).

  27. 27.

    ., ., & Structural characterization of zirconium cations derived from a living Ziegler−Natta polymerization system:  new insights regarding propagation and termination pathways for homogeneous catalysts. J. Am. Chem. Soc. 122, 12909–12910 (2000).

  28. 28.

    & Direct methyl group exchange between cationic zirconium Ziegler−Natta initiators and their living polymers:  ramifications for the production of stereoblock polyolefins. J. Am. Chem. Soc. 123, 10754–10755 (2001).

  29. 29.

    ., & Discrete, multiblock isotactic–atactic stereoblock polypropene microstructures of differing block architectures through programmable stereomodulated living Ziegler–Natta polymerization. Angew. Chem. Int. Ed. 45, 2400–2404 (2006).

  30. 30.

    ., & Bimolecular control over polypropene stereochemical microstructure in a well-defined two-state system and a new fundamental form: stereogradient polypropene. Angew. Chem. Int. Ed. 45, 6140–6144 (2006).

  31. 31.

    & Stereoengineering of poly(1,3-methylenecyclohexane) via two-state living coordination polymerization of 1,6-heptadiene. J. Am. Chem. Soc. 135, 8778–8781 (2013).

  32. 32.

    & Investigation of dynamic intra- and intermolecular processes within a tether-length dependent series of group 4 bimetallic initiators for stereomodulated degenerative transfer living Ziegler–Natta propene polymerization. Adv. Synth. Catal. 350, 439–447 (2008).

  33. 33.

    & Highly efficient, living coordinative chain-transfer polymerization of propene with ZnEt2:  practical production of ultrahigh to very low molecular weight amorphous atactic polypropenes of extremely narrow polydispersity. J. Am. Chem. Soc. 130, 442–443 (2008).

  34. 34.

    ., & Living coordinative chain-transfer polymerization and copolymerization of ethene, α-olefins, and α,ω-nonconjugated dienes using dialkylzinc as “surrogate” chain-growth sites. Macromolecules 41, 7829–7833 (2008).

  35. 35.

    ., ., & Dinuclear bis-propagators for the stereoselective living coordinative chain transfer polymerization of propene. J. Am. Chem. Soc. 135, 2132–2135 (2013).

  36. 36.

    ., & Aufbaureaktion redux: scalable production of precision hydrocarbons from AlR3 (R=Et or iBu) by dialkyl zinc mediated ternary living coordinative chain-transfer polymerization. Angew. Chem. Int. Ed. 49, 1768–1772 (2010).

  37. 37.

    ., ., & Programmable modulation of co-monomer relative reactivities for living coordination polymerization through reversible chain transfer between “tight” and “loose” ion pairs. Angew. Chem. Int. Ed. 49, 9140–9144 (2010).

  38. 38.

    Ex uno plures (“out of one, many”): new paradigms for expanding the range of polyolefins through reversible group transfers. Angew. Chem. Int. Ed. 48, 2464–2472 (2009).

  39. 39.

    ., ., ., ., & Polymerization of ethylene by the electrophilic mixed cyclopentadienylpyridylalkoxide complexes [CpM{NC5H4(CR2O)-2}Cl2] (M=Ti, Zr, R=Ph, Pri). Organometallics 17, 3408–3410 (1998).

  40. 40.

    & Uniqueness and versatility of iminopyrrolyl ligands for transition metal complexes. J. Organomet. Chem. 690, 4414–4423 (2005).

  41. 41.

    ., & Synthesis and characterization of bis(iminopyrrolyl)zirconium complexes. Chem. Lett. 29, 1114–1115 (2000).

  42. 42.

    ., ., & Unusual enhancement of ethylene polymerization activity of benzyl zirconium complexes by benzylation of the imino moiety of 2-(N-aryliminomethyl)pyrrolyl ligand. Chem. Lett. 32, 756–757 (2003).

  43. 43.

    ., & Preparation and characterization of iminopyrrolyl hafnium complexes as catalyst precursors for α-olefin polymerization. J. Mol. Catal. A Chem. 254, 131–137 (2006).

  44. 44.

    & Preparation and characterization of a zwitterionic (iminopyrrolyl)zirconium complex with benzylaluminate anion and its catalytic performance for 1-hexene polymerization. Organometallics 25, 5210–5212 (2006).

  45. 45.

    ., & Isoselective living polymerization of 1-hexene catalyzed by half-metallocene dimethyl complexes of hafnium with bidentate N-substituted (iminomethyl)pyrrolyl ligands. Organometallics 24, 3375–3377 (2005).

  46. 46.

    ., ., & Isospecific polymerization of 1-hexene by C1-symmetric half-metallocene dimethyl complexes of group 4 metals with bidentate N-substituted iminomethylpyrrolyl ligands. Dalton Trans. 42, 9120–9128 (2013).

  47. 47.

    ., & Imino-indolate half-titanocene chlorides: synthesis and their ethylene (co-)polymerization. J. Polym. Sci. A Polym. Chem. 47, 357–372 (2009).

  48. 48.

    & Copolymerization of polar monomers with olefins using transition-metal complexes. Chem. Rev. 100, 1479–1494 (2000).

  49. 49.

    ., ., ., & Synthesis and characterization of phosphine-(thio)phenolate-based half-zirconocenes and their application in ethylene (co-)polymerization. Dalton Trans. 43, 222 (2014).

  50. 50.

    ., ., ., & Monocyclopentadienyl phenoxy-imine and phenoxy-amine complexes of titanium and zirconium and their application as catalysts for 1-alkene polymerization. J. Organomet. Chem. 665, 135–149 (2003).

  51. 51.

    ., ., & Synthesis, structure and ethylene (co)polymerization behavior of new nonbridged half-metallocene-type titanium complexes based on bidentate β-enaminoketonato ligands. Polymer 51, 1921–1925 (2010).

  52. 52.

    ., ., ., & Synthesis and characterization of novel half-metallocene-type group iv complexes containing phosphine oxide–phenolate chelating ligands and their application to ethylene polymerization. Organometallics 30, 4052–4059 (2011).

  53. 53.

    ., ., ., & Monochloro non-bridged half-metallocene-type zirconium complexes containing phosphine oxide-(thio)phenolate chelating ligands as efficient ethylene polymerization catalysts. Dalton Trans. 42, 499 (2013).

  54. 54.

    ., ., ., ., & Syntheses of titanium(IV) complexes with mono-Cp and Schiff base ligands and their catalytic activities for ethylene polymerization and ethylene/1-hexene copolymerization. Macromolecules 35, 4871–4874 (2002).

  55. 55.

    ., ., ., ., ., ., & Monocyclopentadienyl bis(phenoxo-imino) zirconium complexes as precatalyst species for olefin polymerization. Stereospecific methylation of an imino group with formation of a zirconium−amido bond. Organometallics 23, 5324–5331 (2004).

  56. 56.

    ., ., & Ancillary aryloxide ligands in ethylene polymerization catalyst precursors. J. Organomet. Chem. 591, 185–193 (1999).

  57. 57.

    ., & . Half-metallocene zirconium complex bearing tridentate [N,N,O] ligand and its use in homo- and copolymerization of ethylene. Catal. Commun. 42, 113–115 (2013).

  58. 58.

    ., & Hydrazonide titanium derivatives: synthesis, characterization and catalytic activity in olefin polymerization. Molecular structure of [Ti(η5-C5H4SiMe3)Cl(μ-N2CPh2)]2. J. Organomet. Chem. 663, 173–182 (2002).

  59. 59.

    ., & Synthesis and structural analysis of half-titanocenes containing η2-pyrazolato ligands, and their use in catalysis for ethylene polymerization. Inorg. Chem. 48, 5011–5020 (2009).

  60. 60.

    ., & Cyclopentadienyl titanium hydroxylaminato complexes as highly active catalysts for the polymerization of propylene. Chem. Commun. 2152–2154 (2005).

  61. 61.

    ., & Synthesis, structure and ethylene polymerization behavior of titanium phosphinoamide complexes. J. Organomet. Chem. 690, 2941–2946 (2005).

  62. 62.

    ., & Olefin polymerization catalyst derived by activation of a neutral monoalkyl titanium complex with an aminopyrrole ligand using triisobutylaluminum and trityl borate. Chem. Lett. 36, 1030–1031 (2007).

  63. 63.

    ., ., & Studies on the active species in olefin polymerisation generated from phenoxo-amido titanium “chiral-at-metal” compounds. J. Organomet. Chem. 696, 2330–2337 (2011).

  64. 64.

    ., ., ., & Monocyclopentadienyl and ansa-monocyclopentadienylalkoxo complexes of titanium containing the 2,2‘-methylenebis(6-tert-butyl-4-methylphenoxo) ligand. Synthesis, characterization, and polymerization catalyst behavior. Molecular structure of Ti(η5-C5H5)(η2-MBMP)Cl, Ti(η5-C5Me5)(η2-MBMP)Cl, and Ti(η5-C5H4SiMe2-η1-MBMP)Cl2. Organometallics 22, 2694–2704 (2003).

  65. 65.

    ., & New half-sandwich metallocene catalysts for polyethylene and polystyrene. J. Organomet. Chem. 634, 19–24 (2001).

  66. 66.

    ., ., ., & New group 4 half sandwich complexes containing triethanolamine ligand for polyethylene. J. Organomet. Chem. 691, 1121–1125 (2006).

  67. 67.

    ., ., ., & Syndiospecific polymerization of styrene with Cp*TiCl((OCH(R)CH2)2NAr)/MMAO. J. Polym. Sci. A Polym. Chem. 43, 1562–1568 (2005).

  68. 68.

    ., ., ., ., & (Pentamethylcyclopentadienyl)titanatrane: a new class of catalyst for syndiospecific polymerization of styrene. Organometallics 18, 36–39 (1999).

  69. 69.

    & Preparation of syndiotactic poly(4-tert-butyldimethyl-silyloxystyrene) and poly(4-hydroxystyrene). Macromol. Rapid Commun. 21, 1148 (2000).

  70. 70.

    ., ., ., ., ., & New half-metallocene catalysts generating polyethylene with bimodal molecular weight distribution and syndiotactic polystyrene. Macromol. Rapid Commun. 22, 573–578 (2001).

  71. 71.

    ., ., ., & New titanatranes:  characterization and styrene polymerization behavior. Organometallics 21, 1127–1135 (2002).

  72. 72.

    ., ., ., & Half-titanocene complexes bearing dianionic 6-benzimidazolylpyridyl-2-carboximidate ligands: synthesis, characterization, and their ethylene polymerization. J. Polym. Sci. A Polym. Sci. 46, 3396–3410 (2008).

  73. 73.

    ., ., ., ., & N-(2-benzimidazolylquinolin-8-yl)benzamidate half-titanocene chlorides: Synthesis, characterization and their catalytic behavior toward ethylene polymerization. J. Polym. Sci. A Polym. Sci. 47, 3154–3169 (2009).

  74. 74.

    ., ., ., ., & Syntheses, characterization, and the ethylene (Co-)polymerization screening of 2-benzimidazolyl-N-phenylquinoline-8-carboxamide half-titanocene chlorides. Organometallics 29, 732–741 (2010).

  75. 75.

    ., ., & Stereospecific catalysts for the head-to-tail polymerization of propylene to a crystalline syndiotactic polymer. J. Am. Chem. Soc. 84, 1488–1490 (1962).

  76. 76.

    ., & "Living" coordination polymerization of propene initiated by the soluble V(acac)3-Al(C2H5)2Cl system. Macromolecules 12, 814–819 (1979).

  77. 77.

    ., & A perfect initiator for “living” coordination polymerization of propene: Tris(2-methyl-1,3-butanedionato)vanadium/diethylaluminium chloride system. Makromol. Chem. Rapid Commun. 6, 639–642 (1985).

  78. 78.

    ., & Living coordination polymerization of propene with a highly active vanadium-based catalyst. Macromoleules 19, 2896–2900 (1986).

  79. 79.

    ., ., & Living coordination polymerization of propylene and synthesis of tailor-made polymers. Transition Met. Catal. Polym. 2, 182–194 (1988).

  80. 80.

    ., & Synthesis, characterization and reactions of ethylene complexes bearing Ta(η5-C5R5)(η4-buta-1,3-diene) fragments (R = H, Me). J. Organomet. Chem. 502, 19–23 (1995).

  81. 81.

    & ‘Supine’ or ‘prone’ ligands: geometric preference of conjugated diene, 1-azadiene, and 1,4-diazadiene ligands on half-metallocene complexes of early transition metals. J. Organomet. Chem. 621, 224–230 (2001).

  82. 82.

    & Adaptable coordination modes of conjugated 1,3-diene: uniqueness of s-trans coordination. J. Organomet. Chem. 663, 5–12 (2002).

  83. 83.

    ., & Polymerization of ethylene catalyzed by a tantalum system Ta(.eta.3-C5Me5)(.eta.4-diene)(CH3)2/MAO: an isoelectronic analog for group 4 metallocene catalyst (MAO = methylaluminoxane). J. Am. Chem. Soc. 115, 10990–10991 (1993).

  84. 84.

    ., ., ., ., ., & Living polymerization of ethylene catalyzed by diene complexes of niobium and tantalum, M(.eta.5-C5Me5)(.eta.4-diene)X2 and M(.eta.5-C5Me5)(.eta.4-diene)2 (M = Nb and Ta), in the presence of methylaluminoxane. Organometallics 14, 2633–2640 (1995).

  85. 85.

    ., ., ., ., ., ., ., & Unique bonding and geometry in .eta.-cyclopentadienyltantalum-diene complexes. Preparation, x-ray structural analyses, and EHMO calculations. J. Am. Chem. Soc. 107, 2410–2422 (1985).

  86. 86.

    ., ., ., ., & Synthesis and catalysis of novel mono- and bis(diene) complexes of niobium and x-ray structures of binuclear [Nb(.mu.-Cl)(C5H5)(s-cis-butadiene)]2 and mononuclear Nb(C5H5)(s-cis-2,3-dimethylbutadiene)2. J. Am. Chem. Soc. 110, 5008 (1998).

  87. 87.

    ., ., ., ., & Synthesis, x-ray structure and nucleophilic properties of mixed bis(diene)tantalum complexes Ta(.eta.5-C5R5)(.eta.4-C4H6)(.eta.4-C6H10). Organometallics 7, 2266–2273 (1988).

  88. 88.

    Coordination polymerization of polar vinyl monomers by single-site metal catalysts. Chem. Rev. 109, 5157–5214 (2009).

  89. 89.

    ., & Half-metallocene tantalum complexes bearing methyl methacrylate (MMA) and 1,4-diaza-1,3-diene ligands as MMA polymerization catalysts. Angew. Chem. Int. Ed. 40, 960–962 (2001).

  90. 90.

    Olefin polymerization on supported chromium oxide catalysts. Catal. Rev. 3, 145–173 (1970).

  91. 91.

    ., ., ., ., & Chromocene catalysts for ethylene polymerization: scope of the polymerization. J. Polym. Sci. A-1 10, 2621 (1972).

  92. 92.

    ., & Chromocene-based catalysts for ethylene polymerization: kinetic parameters. J. Polym. Sci. Polym. Chem. Ed. 11, 413 (1973).

  93. 93.

    ., & Correlations between structure, magnetism, and polymerization activity of paramagnetic benzylchromium complexes. Chem. Eur. J. 1, 199–203 (1995).

  94. 94.

    ., ., ., & Paramagnetic (Benzyl)chromium complexes as homogeneous ethylene polymerization catalysts. Organometallics 14, 738–745 (1995).

  95. 95.

    ., ., & Constrained geometry chromium catalysts for olefin polymerization. Organometallics 15, 5284–5286 (1996).

  96. 96.

    ., ., ., & Structure and reactivity of trimethylsilylmethyl complexes of chromium, including the 13-electron alkyl Cp*Cr(CH2SiMe3)2. Organometallics 17, 5477–5485 (1998).

  97. 97.

    Homogeneous chromium catalysts for olefin polymerization. Eur. J. Inorg. Chem. 15–24 (1998).

  98. 98.

    ., ., ., ., ., & A five-coordinate chromium alkyl complex stabilised by salicylaldiminato ligands. J. Chem. Soc. Dalton Trans. 1969–1971 (2000).

  99. 99.

    ., ., ., ., & Donor-ligand-substituted cyclopentadienylchromium(III) complexes:  a new class of alkene polymerization catalyst. 1. Amino-substituted systems. Organometallics 19, 388–402 (2000).

  100. 100.

    ., ., ., ., & The (Ph)2nacnac ligand in organochromium chemistry. Organometallics 21, 952–960 (2002).

  101. 101.

    & A neutral chromium(III) catalyst for the living “Aufbaureaktion”. Angew. Chem. Int. Ed. 43, 2263–2266 (2004).

  102. 102.

    ., ., ., & A chromium catalyst for the polymerization of ethylene as a homogeneous model for the phillips catalyst. J. Am. Chem. Soc. 127, 1082–1083 (2005).

  103. 103.

    & Cationic chromium(III) alkyls as olefin polymerization catalysts. J. Am. Chem. Soc. 110, 5902–5903 (1988).

  104. 104.

    ., ., ., & Paramagnetic alkylchromium compounds as homogeneous catalysts for the polymerization of ethylene. J. Am. Chem. Soc. 113, 893–902 (1991).

  105. 105.

    ., ., & A facile access to CpCr (acac)Cl and related systems. J. Organomet. Chem. 553, 477–479 (1998).

  106. 106.

    ., ., ., ., & Highly active half-metallocene chromium(III) catalysts for ethylene polymerization activated by trialkylaluminum. J. Am. Chem. Soc. 129, 2236–2237 (2007).

  107. 107.

    ., ., ., & Synthesis, structures and ethylene polymerization behavior of half-metallocene chromium(III) catalysts bearing salicylaldiminato ligands. New J. Chem. 34, 2979–2987 (2010).

  108. 108.

    ., ., ., ., ., & Large ultra-high molecular weight polyethylene spherical particles produced by AlR3 activated half-sandwich chromium(III) catalysts. Dalton Trans. 40, 10184 (2011).

  109. 109.

    & Half-sandwich chromium(III) complexes bearing β-ketoiminato and β-diketiminate ligands as catalysts for ethylene polymerization. Dalton Trans. 38, 767–769 (2009).

  110. 110.

    ., & Half-sandwich chromium(III) catalysts bearing hydroxyindanimine ligands for ethylene polymerization. Organometallics 28, 4170–4174 (2009).

  111. 111.

    ., & Cyclopentadienylmolybdenum(II) and -(III) complexes containing diene and allyl ligands. 1. Isomeric preferences and isomerization rates in a pair of redox-related organometallic complexes. J. Am. Chem. Soc. 119, 4453–4464 (1997).

  112. 112.

    ., & Stable 17-electron Mo(III) complexes containing alkyl ligands. Inorg. Chem. Commun. 2, 95–97 (1999).

  113. 113.

    ., & Dialkyl(butadiene)cyclopentadienylmolybdenum(III) complexes. Synthesis, characterization, and reactivity. Organometallics 19, 3842–3853 (2000).

  114. 114.

    & Diene-containing half-sandwich MoIII complexes as ethylene polymerization catalysts: experimental and theoretical studies. Chem. Eur. J. 7, 4572–4583 (2001).

  115. 115.

    ., ., ., ., & Homolytic bond strengths and formation rates in half-sandwich chromium alkyl complexes: relevance for controlled radical polymerization. Angew. Chem. Int. Ed. 47, 6069–6072 (2008).

  116. 116.

    ., ., ., ., & Cyclopentadienyl chromium β-diketiminate complexes: initiators, ligand steric effects, and deactivation processes in the controlled radical polymerization of vinyl acetate. Organometallics 29, 167–176 (2010).

  117. 117.

    ., ., ., & Controlled radical polymerization of vinyl acetate with cyclopentadienyl chromium β-diketiminate complexes: ATRP vs OMRP. Organometallics 29, 3125–3132 (2010).

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Acknowledgements

HT acknowledges financial support by a Grant-in-Aid for Young Scientists (A). KY expresses his special thanks for the financial support provided by the JSPS Research Fellowship for Young Scientists.

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  1. Department of Chemistry, Graduate School of Engineering Science, Osaka University, and CREST, JST, Osaka, Japan

    • Hayato Tsurugi
    • , Keishi Yamamoto
    • , Raphaël Rochat
    •  & Kazushi Mashima

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Correspondence to Kazushi Mashima.

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https://doi.org/10.1038/pj.2014.82

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