Distinctive Stereochemically Linked Cooperative Effects in Bimetallic Titanium Olefin Polymerization Catalysts

Shaofeng Liu; Anna M. Invergo; Jennifer P. McInnis; Aidan R. Mouat; Alessandro Motta; Tracy L. Lohr; Massimiliano Delferro; Tobin J. Marks

doi:10.1021/acs.organomet.7b00641

Distinctive Stereochemically Linked Cooperative Effects in Bimetallic Titanium Olefin Polymerization Catalysts

Shaofeng Liu, Anna M. Invergo, Jennifer P. McInnis, Aidan R. Mouat, Alessandro Motta, Tracy L. Lohr^*, Massimiliano Delferro, Tobin J. Marks

^*Corresponding author for this work

Chemistry

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39 Scopus citations

Abstract

The complex (μ-Me₂C-3,3′){(n⁵-cyclopentadienyl)[1-Me₂Si-(^tBuN)](TiMe₂)}₂ (3) was prepared as a new binuclear catalyst motif for homogeneous olefin polymerization. Complex 3 exists as rac-3 and meso-3 diastereomers, which can be separated and characterized by solution NMR spectroscopy and single-crystal X-ray diffraction. While meso-3 has high thermal stability, rac-3 undergoes thermolysis in solution to quantitatively form the dimeric methylidene complex (μ-Me₂C-3,3′){(n⁵-cyclopentadienyl)[1-Me₂Si(^tBuN)][(μ-CH₂)Ti]}₂ (rac-4). Activation of rac-3 and meso-3 with 1 equiv of Ph₃C⁺B(C₆F₅)₄^- yields [(μ-CMe₂-3,3′){( n ⁵-cyclopentadienyl)[1-Me₂Si(^tBuN)]}₂(μ-CH₂)(μ-CH₃)Ti₂]⁺B(C₆F₅)₄^- (5; rac-5 and meso-5, respectively). Interestingly, meso-5 is stable in the presence of an additional 1 equiv of Ph₃C⁺B(C₆F₅)₄^-, while rac-5 reacts to yield rac-[(μ-CMe₂-3,3′){( n ⁵-cyclopentadienyl)[1-Me₂Si(^tBuN)]}₂(μ-CH₂)[(TiCH₃)(Ti- n ¹-Ph₃C)]²⁺[B(C₆F₅)₄^-]₂ (rac-6) as indicated by multinuclear NMR spectroscopy and DFT computation. meso-3 reacts with 2 equiv of B(C₆F₅)₃ to yield meso-[(μ-CMe₂-3,3′){( n n ⁵-cyclopentadienyl)[1-Me₂Si(^tBuN)]}₂(μ-CH₂)(μ-CH₃)Ti₂]⁺MeB(C₆F₅)₃^- (meso-7) containing the same meso-5 cation but with a MeB(C₆F₅)₃^-counteranion. These findings, along with catalytic results, indicate that rac-3 and meso-3 remain structurally intact during polymerization, consistent with the observed diastereoselectivity effects. Under identical ethylene/1-octene copolymerization conditions, only activated bimetallic rac-3 produces appreciable polymer, with meso-3 exhibiting low activity, but both yield polymer with a branch density >2× that of the monometallic control [(3-^tBu-C₅H₃)SiMe₂N^tBu]TiMe₂ (Ti₁). In ethylene/styrene copolymerizations, rac-3 produces polymers with 3.1× higher M_n and 2.1× greater styrene incorporation versus Ti₁, while meso-3 catalyzes only ethylene-free styrene homopolymerization. In 1-octene homopolymerizations, meso-3 + B(C₆F₅)₃ (i.e., meso-7) produces highly isotactic poly-1-octene (mmmm 91.7%), while rac-3 + Ph₃C⁺B(C₆F₅)₄^- (i.e., rac-5), rac-3 + B(C₆F₅)₃ (i.e., rac-7), and meso-3 + Ph₃C⁺B(C₆F₅)₄^- (i.e., meso-5) produce only atactic poly-1-octene. These bimetallic polymerization catalysts exhibit distinctive cooperative effects influencing product M_n, tacticity, and comonomer selection, demonstrating that binuclear catalyst stereochemical factors are significant.

Original language	English (US)
Pages (from-to)	4403-4421
Number of pages	19
Journal	Organometallics
Volume	36
Issue number	22
DOIs	https://doi.org/10.1021/acs.organomet.7b00641
State	Published - Nov 27 2017

Funding

This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Award Number DOE DE-FG02-03-ER154757 for C−C bond-forming catalysis (A.M.I., A.R.M.) and by NSF CHE-1464488 for cooperative catalyst design (T.L.L., S.L., J.P.M.), whose support is gratefully acknowledged. The purchase of the NMR instrumentation at IMSERC at Northwestern University was supported by the NSF (CHE-1048773). Computational resources supporting this work were provided by the Northwestern University Quest High Performance Computing cluster (M.D. and T.L.L.) and CINECA award N. HP10CBHAYD 2014 under the ISCRA initiative (A.M.). We also thank Albemarle Corp. for the generous gifts of Ph3C+B(C6F5)4−and B(C6F5)3.

ASJC Scopus subject areas

Physical and Theoretical Chemistry
Organic Chemistry
Inorganic Chemistry

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10.1021/acs.organomet.7b00641

Cite this

@article{3327d3f71b664dc19edfbbf670cf0a7d,

title = "Distinctive Stereochemically Linked Cooperative Effects in Bimetallic Titanium Olefin Polymerization Catalysts",

abstract = "The complex (μ-Me2C-3,3′){(n5-cyclopentadienyl)[1-Me2Si-(tBuN)](TiMe2)}2 (3) was prepared as a new binuclear catalyst motif for homogeneous olefin polymerization. Complex 3 exists as rac-3 and meso-3 diastereomers, which can be separated and characterized by solution NMR spectroscopy and single-crystal X-ray diffraction. While meso-3 has high thermal stability, rac-3 undergoes thermolysis in solution to quantitatively form the dimeric methylidene complex (μ-Me2C-3,3′){(n5-cyclopentadienyl)[1-Me2Si(tBuN)][(μ-CH2)Ti]}2 (rac-4). Activation of rac-3 and meso-3 with 1 equiv of Ph3C+B(C6F5)4- yields [(μ-CMe2-3,3′){( n 5-cyclopentadienyl)[1-Me2Si(tBuN)]}2(μ-CH2)(μ-CH3)Ti2]+B(C6F5)4- (5; rac-5 and meso-5, respectively). Interestingly, meso-5 is stable in the presence of an additional 1 equiv of Ph3C+B(C6F5)4-, while rac-5 reacts to yield rac-[(μ-CMe2-3,3′){( n 5-cyclopentadienyl)[1-Me2Si(tBuN)]}2(μ-CH2)[(TiCH3)(Ti- n 1-Ph3C)]2+[B(C6F5)4-]2 (rac-6) as indicated by multinuclear NMR spectroscopy and DFT computation. meso-3 reacts with 2 equiv of B(C6F5)3 to yield meso-[(μ-CMe2-3,3′){( n n 5-cyclopentadienyl)[1-Me2Si(tBuN)]}2(μ-CH2)(μ-CH3)Ti2]+MeB(C6F5)3- (meso-7) containing the same meso-5 cation but with a MeB(C6F5)3-counteranion. These findings, along with catalytic results, indicate that rac-3 and meso-3 remain structurally intact during polymerization, consistent with the observed diastereoselectivity effects. Under identical ethylene/1-octene copolymerization conditions, only activated bimetallic rac-3 produces appreciable polymer, with meso-3 exhibiting low activity, but both yield polymer with a branch density >2× that of the monometallic control [(3-tBu-C5H3)SiMe2NtBu]TiMe2 (Ti1). In ethylene/styrene copolymerizations, rac-3 produces polymers with 3.1× higher Mn and 2.1× greater styrene incorporation versus Ti1, while meso-3 catalyzes only ethylene-free styrene homopolymerization. In 1-octene homopolymerizations, meso-3 + B(C6F5)3 (i.e., meso-7) produces highly isotactic poly-1-octene (mmmm 91.7%), while rac-3 + Ph3C+B(C6F5)4- (i.e., rac-5), rac-3 + B(C6F5)3 (i.e., rac-7), and meso-3 + Ph3C+B(C6F5)4- (i.e., meso-5) produce only atactic poly-1-octene. These bimetallic polymerization catalysts exhibit distinctive cooperative effects influencing product Mn, tacticity, and comonomer selection, demonstrating that binuclear catalyst stereochemical factors are significant.",

author = "Shaofeng Liu and Invergo, {Anna M.} and McInnis, {Jennifer P.} and Mouat, {Aidan R.} and Alessandro Motta and Lohr, {Tracy L.} and Massimiliano Delferro and Marks, {Tobin J.}",

note = "Funding Information: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Award Number DOE DE-FG02-03-ER154757 for C−C bond-forming catalysis (A.M.I., A.R.M.) and by NSF CHE-1464488 for cooperative catalyst design (T.L.L., S.L., J.P.M.), whose support is gratefully acknowledged. The purchase of the NMR instrumentation at IMSERC at Northwestern University was supported by the NSF (CHE-1048773). Computational resources supporting this work were provided by the Northwestern University Quest High Performance Computing cluster (M.D. and T.L.L.) and CINECA award N. HP10CBHAYD 2014 under the ISCRA initiative (A.M.). We also thank Albemarle Corp. for the generous gifts of Ph3C+B(C6F5)4−and B(C6F5)3. Publisher Copyright: {\textcopyright} 2017 American Chemical Society.",

year = "2017",

month = nov,

day = "27",

doi = "10.1021/acs.organomet.7b00641",

language = "English (US)",

volume = "36",

pages = "4403--4421",

journal = "Organometallics",

issn = "0276-7333",

publisher = "American Chemical Society",

number = "22",

}

TY - JOUR

T1 - Distinctive Stereochemically Linked Cooperative Effects in Bimetallic Titanium Olefin Polymerization Catalysts

AU - Liu, Shaofeng

AU - Invergo, Anna M.

AU - McInnis, Jennifer P.

AU - Mouat, Aidan R.

AU - Motta, Alessandro

AU - Lohr, Tracy L.

AU - Delferro, Massimiliano

AU - Marks, Tobin J.

N1 - Funding Information: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Award Number DOE DE-FG02-03-ER154757 for C−C bond-forming catalysis (A.M.I., A.R.M.) and by NSF CHE-1464488 for cooperative catalyst design (T.L.L., S.L., J.P.M.), whose support is gratefully acknowledged. The purchase of the NMR instrumentation at IMSERC at Northwestern University was supported by the NSF (CHE-1048773). Computational resources supporting this work were provided by the Northwestern University Quest High Performance Computing cluster (M.D. and T.L.L.) and CINECA award N. HP10CBHAYD 2014 under the ISCRA initiative (A.M.). We also thank Albemarle Corp. for the generous gifts of Ph3C+B(C6F5)4−and B(C6F5)3. Publisher Copyright: © 2017 American Chemical Society.

PY - 2017/11/27

Y1 - 2017/11/27

N2 - The complex (μ-Me2C-3,3′){(n5-cyclopentadienyl)[1-Me2Si-(tBuN)](TiMe2)}2 (3) was prepared as a new binuclear catalyst motif for homogeneous olefin polymerization. Complex 3 exists as rac-3 and meso-3 diastereomers, which can be separated and characterized by solution NMR spectroscopy and single-crystal X-ray diffraction. While meso-3 has high thermal stability, rac-3 undergoes thermolysis in solution to quantitatively form the dimeric methylidene complex (μ-Me2C-3,3′){(n5-cyclopentadienyl)[1-Me2Si(tBuN)][(μ-CH2)Ti]}2 (rac-4). Activation of rac-3 and meso-3 with 1 equiv of Ph3C+B(C6F5)4- yields [(μ-CMe2-3,3′){( n 5-cyclopentadienyl)[1-Me2Si(tBuN)]}2(μ-CH2)(μ-CH3)Ti2]+B(C6F5)4- (5; rac-5 and meso-5, respectively). Interestingly, meso-5 is stable in the presence of an additional 1 equiv of Ph3C+B(C6F5)4-, while rac-5 reacts to yield rac-[(μ-CMe2-3,3′){( n 5-cyclopentadienyl)[1-Me2Si(tBuN)]}2(μ-CH2)[(TiCH3)(Ti- n 1-Ph3C)]2+[B(C6F5)4-]2 (rac-6) as indicated by multinuclear NMR spectroscopy and DFT computation. meso-3 reacts with 2 equiv of B(C6F5)3 to yield meso-[(μ-CMe2-3,3′){( n n 5-cyclopentadienyl)[1-Me2Si(tBuN)]}2(μ-CH2)(μ-CH3)Ti2]+MeB(C6F5)3- (meso-7) containing the same meso-5 cation but with a MeB(C6F5)3-counteranion. These findings, along with catalytic results, indicate that rac-3 and meso-3 remain structurally intact during polymerization, consistent with the observed diastereoselectivity effects. Under identical ethylene/1-octene copolymerization conditions, only activated bimetallic rac-3 produces appreciable polymer, with meso-3 exhibiting low activity, but both yield polymer with a branch density >2× that of the monometallic control [(3-tBu-C5H3)SiMe2NtBu]TiMe2 (Ti1). In ethylene/styrene copolymerizations, rac-3 produces polymers with 3.1× higher Mn and 2.1× greater styrene incorporation versus Ti1, while meso-3 catalyzes only ethylene-free styrene homopolymerization. In 1-octene homopolymerizations, meso-3 + B(C6F5)3 (i.e., meso-7) produces highly isotactic poly-1-octene (mmmm 91.7%), while rac-3 + Ph3C+B(C6F5)4- (i.e., rac-5), rac-3 + B(C6F5)3 (i.e., rac-7), and meso-3 + Ph3C+B(C6F5)4- (i.e., meso-5) produce only atactic poly-1-octene. These bimetallic polymerization catalysts exhibit distinctive cooperative effects influencing product Mn, tacticity, and comonomer selection, demonstrating that binuclear catalyst stereochemical factors are significant.

AB - The complex (μ-Me2C-3,3′){(n5-cyclopentadienyl)[1-Me2Si-(tBuN)](TiMe2)}2 (3) was prepared as a new binuclear catalyst motif for homogeneous olefin polymerization. Complex 3 exists as rac-3 and meso-3 diastereomers, which can be separated and characterized by solution NMR spectroscopy and single-crystal X-ray diffraction. While meso-3 has high thermal stability, rac-3 undergoes thermolysis in solution to quantitatively form the dimeric methylidene complex (μ-Me2C-3,3′){(n5-cyclopentadienyl)[1-Me2Si(tBuN)][(μ-CH2)Ti]}2 (rac-4). Activation of rac-3 and meso-3 with 1 equiv of Ph3C+B(C6F5)4- yields [(μ-CMe2-3,3′){( n 5-cyclopentadienyl)[1-Me2Si(tBuN)]}2(μ-CH2)(μ-CH3)Ti2]+B(C6F5)4- (5; rac-5 and meso-5, respectively). Interestingly, meso-5 is stable in the presence of an additional 1 equiv of Ph3C+B(C6F5)4-, while rac-5 reacts to yield rac-[(μ-CMe2-3,3′){( n 5-cyclopentadienyl)[1-Me2Si(tBuN)]}2(μ-CH2)[(TiCH3)(Ti- n 1-Ph3C)]2+[B(C6F5)4-]2 (rac-6) as indicated by multinuclear NMR spectroscopy and DFT computation. meso-3 reacts with 2 equiv of B(C6F5)3 to yield meso-[(μ-CMe2-3,3′){( n n 5-cyclopentadienyl)[1-Me2Si(tBuN)]}2(μ-CH2)(μ-CH3)Ti2]+MeB(C6F5)3- (meso-7) containing the same meso-5 cation but with a MeB(C6F5)3-counteranion. These findings, along with catalytic results, indicate that rac-3 and meso-3 remain structurally intact during polymerization, consistent with the observed diastereoselectivity effects. Under identical ethylene/1-octene copolymerization conditions, only activated bimetallic rac-3 produces appreciable polymer, with meso-3 exhibiting low activity, but both yield polymer with a branch density >2× that of the monometallic control [(3-tBu-C5H3)SiMe2NtBu]TiMe2 (Ti1). In ethylene/styrene copolymerizations, rac-3 produces polymers with 3.1× higher Mn and 2.1× greater styrene incorporation versus Ti1, while meso-3 catalyzes only ethylene-free styrene homopolymerization. In 1-octene homopolymerizations, meso-3 + B(C6F5)3 (i.e., meso-7) produces highly isotactic poly-1-octene (mmmm 91.7%), while rac-3 + Ph3C+B(C6F5)4- (i.e., rac-5), rac-3 + B(C6F5)3 (i.e., rac-7), and meso-3 + Ph3C+B(C6F5)4- (i.e., meso-5) produce only atactic poly-1-octene. These bimetallic polymerization catalysts exhibit distinctive cooperative effects influencing product Mn, tacticity, and comonomer selection, demonstrating that binuclear catalyst stereochemical factors are significant.

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Distinctive Stereochemically Linked Cooperative Effects in Bimetallic Titanium Olefin Polymerization Catalysts

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CCDC 1570299: Experimental Crystal Structure Determination

CCDC 1570303: Experimental Crystal Structure Determination

CCDC 1570295: Experimental Crystal Structure Determination

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Distinctive Stereochemically Linked Cooperative Effects in Bimetallic Titanium Olefin Polymerization Catalysts

Abstract

Funding

ASJC Scopus subject areas

Access to Document

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Datasets

CCDC 1570299: Experimental Crystal Structure Determination

CCDC 1570303: Experimental Crystal Structure Determination

CCDC 1570295: Experimental Crystal Structure Determination

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