Very large cooperative effects in heterobimetallic titanium-chromium catalysts for ethylene polymerization/copolymerization

Shaofeng Liu; Alessandro Motta; Aidan R. Mouat; Massimiliano Delferro; Tobin J. Marks

doi:10.1021/ja5046742

Very large cooperative effects in heterobimetallic titanium-chromium catalysts for ethylene polymerization/copolymerization

Shaofeng Liu, Alessandro Motta, Aidan R. Mouat, Massimiliano Delferro^*, Tobin J. Marks

^*Corresponding author for this work

Chemistry

Research output: Contribution to journal › Article › peer-review

118 Scopus citations

Abstract

The heterobimetallic complexes, (Î•⁵-indenyl)[1- Me₂Si(^tBuN)TiCl₂]-3-C_nH _2n-[N,N-bis(2-(ethylthio)ethyl)amine]CrCl₃ (n = 0, Ti-C₀-Cr^SNS; n = 2, Ti-C₂-Cr^SNS; n = 6, Ti-C₆-Cr^SNS), (Î•⁵-indenyl)[1- Me₂Si(^tBuN)TiCl₂]-3-C₂H ₄-[N,N-bis((o-OMe-C₆H₄)₂P)amine] CrCl₃ (Ti-C₂-Cr^PNP), and (Î• ⁵-indenyl)[1-Me₂Si(^tBuN)TiCl ₂]-3-C₂H₄-[N,N-bis((diethylamine)ethyl)-amine] CrCl₃ (Ti-C₂-Cr^NNN), are synthesized, fully characterized, and employed as olefin polymerization catalysts. With ethylene as the feed and MAO as cocatalyst/activator, SNS-based complexes Ti-C ₀-Cr^SNS, Ti-C₂-Cr^SNS, and Ti-C ₆-Cr^SNS afford linear low-density polyethylenes (LLDPEs) with exclusive n-butyl branches (6.8-25.8 branches/1000 C), while under identical polymerization conditions Ti-C₂-Cr^PNP and Ti-C₂-Cr^NNN produce polyethylenes with heterogeneous branching (C₂, C₄, and C_{â‰¥ 6}) or negligible branching, respectively. Under identical ethylene polymerization conditions, Ti-C₀-Cr^SNS produces polyethylenes with higher activity (4.5× and 6.1×, respectively), M_n (1.3× and 1.8×, respectively), and branch density (1.4× and 3.8×, respectively), than Ti-C₂-Cr^SNS and Ti-C ₆-Cr^SNS. Versus a CGC^EtTi + SNSCr tandem catalyst, Ti-C₀-Cr^SNS yields polyethylene with somewhat lower activity, but with 22.6× higher M_n and 4.0× greater branching density under identical conditions. In ethylene +1-pentene competition experiments, Ti-C₀-Cr^SNS yields 5.5% n-propyl branches and 94.5% n-butyl branches at [1-pentene] = 0.1 M, and the estimated effective local concentration of 1-hexene is ∼8.6 M. In contrast, the tandem CGC^EtTi + SNSCr system yields 91.0% n-propyl branches under identical reaction conditions. The homopolymerization and 1-pentene competition results argue that close Ti···Cr spatial proximity together with weak C-H···Ti and C-H···S interactions significantly influence relative 1-hexene enchainment and chain transfer rates, supported by DFT computation, and that such effects are conversion insensitive but cocatalyst and solvent sensitive.

Original language	English (US)
Pages (from-to)	10460-10469
Number of pages	10
Journal	Journal of the American Chemical Society
Volume	136
Issue number	29
DOIs	https://doi.org/10.1021/ja5046742
State	Published - Jul 23 2014

ASJC Scopus subject areas

General Chemistry
Biochemistry
Catalysis
Colloid and Surface Chemistry

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10.1021/ja5046742

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@article{8fea080498e6486aafce164c2c84c7dd,

title = "Very large cooperative effects in heterobimetallic titanium-chromium catalysts for ethylene polymerization/copolymerization",

abstract = "The heterobimetallic complexes, ({\^I}•5-indenyl)[1- Me2Si(tBuN)TiCl2]-3-CnH 2n-[N,N-bis(2-(ethylthio)ethyl)amine]CrCl3 (n = 0, Ti-C0-CrSNS; n = 2, Ti-C2-CrSNS; n = 6, Ti-C6-CrSNS), ({\^I}•5-indenyl)[1- Me2Si(tBuN)TiCl2]-3-C2H 4-[N,N-bis((o-OMe-C6H4)2P)amine] CrCl3 (Ti-C2-CrPNP), and ({\^I}• 5-indenyl)[1-Me2Si(tBuN)TiCl 2]-3-C2H4-[N,N-bis((diethylamine)ethyl)-amine] CrCl3 (Ti-C2-CrNNN), are synthesized, fully characterized, and employed as olefin polymerization catalysts. With ethylene as the feed and MAO as cocatalyst/activator, SNS-based complexes Ti-C 0-CrSNS, Ti-C2-CrSNS, and Ti-C 6-CrSNS afford linear low-density polyethylenes (LLDPEs) with exclusive n-butyl branches (6.8-25.8 branches/1000 C), while under identical polymerization conditions Ti-C2-CrPNP and Ti-C2-CrNNN produce polyethylenes with heterogeneous branching (C2, C4, and C{\^a}‰¥ 6) or negligible branching, respectively. Under identical ethylene polymerization conditions, Ti-C0-CrSNS produces polyethylenes with higher activity (4.5× and 6.1×, respectively), Mn (1.3× and 1.8×, respectively), and branch density (1.4× and 3.8×, respectively), than Ti-C2-CrSNS and Ti-C 6-CrSNS. Versus a CGCEtTi + SNSCr tandem catalyst, Ti-C0-CrSNS yields polyethylene with somewhat lower activity, but with 22.6× higher Mn and 4.0× greater branching density under identical conditions. In ethylene +1-pentene competition experiments, Ti-C0-CrSNS yields 5.5% n-propyl branches and 94.5% n-butyl branches at [1-pentene] = 0.1 M, and the estimated effective local concentration of 1-hexene is ∼8.6 M. In contrast, the tandem CGCEtTi + SNSCr system yields 91.0% n-propyl branches under identical reaction conditions. The homopolymerization and 1-pentene competition results argue that close Ti···Cr spatial proximity together with weak C-H···Ti and C-H···S interactions significantly influence relative 1-hexene enchainment and chain transfer rates, supported by DFT computation, and that such effects are conversion insensitive but cocatalyst and solvent sensitive.",

author = "Shaofeng Liu and Alessandro Motta and Mouat, {Aidan R.} and Massimiliano Delferro and Marks, {Tobin J.}",

year = "2014",

month = jul,

day = "23",

doi = "10.1021/ja5046742",

language = "English (US)",

volume = "136",

pages = "10460--10469",

journal = "Journal of the American Chemical Society",

issn = "0002-7863",

publisher = "American Chemical Society",

number = "29",

}

TY - JOUR

T1 - Very large cooperative effects in heterobimetallic titanium-chromium catalysts for ethylene polymerization/copolymerization

AU - Liu, Shaofeng

AU - Motta, Alessandro

AU - Mouat, Aidan R.

AU - Delferro, Massimiliano

AU - Marks, Tobin J.

PY - 2014/7/23

Y1 - 2014/7/23

N2 - The heterobimetallic complexes, (Î•5-indenyl)[1- Me2Si(tBuN)TiCl2]-3-CnH 2n-[N,N-bis(2-(ethylthio)ethyl)amine]CrCl3 (n = 0, Ti-C0-CrSNS; n = 2, Ti-C2-CrSNS; n = 6, Ti-C6-CrSNS), (Î•5-indenyl)[1- Me2Si(tBuN)TiCl2]-3-C2H 4-[N,N-bis((o-OMe-C6H4)2P)amine] CrCl3 (Ti-C2-CrPNP), and (Î• 5-indenyl)[1-Me2Si(tBuN)TiCl 2]-3-C2H4-[N,N-bis((diethylamine)ethyl)-amine] CrCl3 (Ti-C2-CrNNN), are synthesized, fully characterized, and employed as olefin polymerization catalysts. With ethylene as the feed and MAO as cocatalyst/activator, SNS-based complexes Ti-C 0-CrSNS, Ti-C2-CrSNS, and Ti-C 6-CrSNS afford linear low-density polyethylenes (LLDPEs) with exclusive n-butyl branches (6.8-25.8 branches/1000 C), while under identical polymerization conditions Ti-C2-CrPNP and Ti-C2-CrNNN produce polyethylenes with heterogeneous branching (C2, C4, and Câ‰¥ 6) or negligible branching, respectively. Under identical ethylene polymerization conditions, Ti-C0-CrSNS produces polyethylenes with higher activity (4.5× and 6.1×, respectively), Mn (1.3× and 1.8×, respectively), and branch density (1.4× and 3.8×, respectively), than Ti-C2-CrSNS and Ti-C 6-CrSNS. Versus a CGCEtTi + SNSCr tandem catalyst, Ti-C0-CrSNS yields polyethylene with somewhat lower activity, but with 22.6× higher Mn and 4.0× greater branching density under identical conditions. In ethylene +1-pentene competition experiments, Ti-C0-CrSNS yields 5.5% n-propyl branches and 94.5% n-butyl branches at [1-pentene] = 0.1 M, and the estimated effective local concentration of 1-hexene is ∼8.6 M. In contrast, the tandem CGCEtTi + SNSCr system yields 91.0% n-propyl branches under identical reaction conditions. The homopolymerization and 1-pentene competition results argue that close Ti···Cr spatial proximity together with weak C-H···Ti and C-H···S interactions significantly influence relative 1-hexene enchainment and chain transfer rates, supported by DFT computation, and that such effects are conversion insensitive but cocatalyst and solvent sensitive.

AB - The heterobimetallic complexes, (Î•5-indenyl)[1- Me2Si(tBuN)TiCl2]-3-CnH 2n-[N,N-bis(2-(ethylthio)ethyl)amine]CrCl3 (n = 0, Ti-C0-CrSNS; n = 2, Ti-C2-CrSNS; n = 6, Ti-C6-CrSNS), (Î•5-indenyl)[1- Me2Si(tBuN)TiCl2]-3-C2H 4-[N,N-bis((o-OMe-C6H4)2P)amine] CrCl3 (Ti-C2-CrPNP), and (Î• 5-indenyl)[1-Me2Si(tBuN)TiCl 2]-3-C2H4-[N,N-bis((diethylamine)ethyl)-amine] CrCl3 (Ti-C2-CrNNN), are synthesized, fully characterized, and employed as olefin polymerization catalysts. With ethylene as the feed and MAO as cocatalyst/activator, SNS-based complexes Ti-C 0-CrSNS, Ti-C2-CrSNS, and Ti-C 6-CrSNS afford linear low-density polyethylenes (LLDPEs) with exclusive n-butyl branches (6.8-25.8 branches/1000 C), while under identical polymerization conditions Ti-C2-CrPNP and Ti-C2-CrNNN produce polyethylenes with heterogeneous branching (C2, C4, and Câ‰¥ 6) or negligible branching, respectively. Under identical ethylene polymerization conditions, Ti-C0-CrSNS produces polyethylenes with higher activity (4.5× and 6.1×, respectively), Mn (1.3× and 1.8×, respectively), and branch density (1.4× and 3.8×, respectively), than Ti-C2-CrSNS and Ti-C 6-CrSNS. Versus a CGCEtTi + SNSCr tandem catalyst, Ti-C0-CrSNS yields polyethylene with somewhat lower activity, but with 22.6× higher Mn and 4.0× greater branching density under identical conditions. In ethylene +1-pentene competition experiments, Ti-C0-CrSNS yields 5.5% n-propyl branches and 94.5% n-butyl branches at [1-pentene] = 0.1 M, and the estimated effective local concentration of 1-hexene is ∼8.6 M. In contrast, the tandem CGCEtTi + SNSCr system yields 91.0% n-propyl branches under identical reaction conditions. The homopolymerization and 1-pentene competition results argue that close Ti···Cr spatial proximity together with weak C-H···Ti and C-H···S interactions significantly influence relative 1-hexene enchainment and chain transfer rates, supported by DFT computation, and that such effects are conversion insensitive but cocatalyst and solvent sensitive.

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Very large cooperative effects in heterobimetallic titanium-chromium catalysts for ethylene polymerization/copolymerization

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CCDC 1424305: Experimental Crystal Structure Determination

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Very large cooperative effects in heterobimetallic titanium-chromium catalysts for ethylene polymerization/copolymerization

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CCDC 1424305: Experimental Crystal Structure Determination

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