Transition Metal‐Catalyzed and MAO‐Assisted Olefin Polymerization. Cyclic Isomers of Sinn’s Dimer Are Excellent Ligands in Iron Complexes and Great Methylating Reagents

Kaidi Yang; Rainer Glaser

doi:10.3390/catal12030312

Transition Metal‐Catalyzed and MAO‐Assisted Olefin Polymerization. Cyclic Isomers of Sinn’s Dimer Are Excellent Ligands in Iron Complexes and Great Methylating Reagents

Kaidi Yang
, Rainer Glaser

Chemistry

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

Abstract

Methylaluminoxane (MAO) is the most commonly used co&hyphen;catalyst for transition metalcatalyzed olefin polymerization, but the structures of MAO species and their catalytic functions remain topics of intensive study. We are interested in MAO&hyphen;assisted polymerization with catalysts L(R 2 )FeCl 2 (L = tridentate pyridine&hyphen;2,6&hyphen;diyldimethanimine; imine&hyphen;R = Me, Ph). It is our hypothesis that the MAO species is not merely enabling Fe−Me bond formation but functions as an integral part of the active catalyst, a MAO adduct of the Fe&hyphen;precatalyst [L(R 2 )FeCl] + . In this paper, we explored the possible structures of acyclic and cyclic MAO species and their complexation with pre&hyphen;catalysts [L(R 2 )FeCl] + using quantum chemical approaches (MP2 and DFT). We report absolute and relative oxophilicities associated with the Fe←O(MAO) adduct formation and provide compelling evidence that oxygen of an acyclic MAO species (i.e., O(AlMe 2 ) 2 , 4) cannot compete with the O&hyphen;donor in cyclic MAO species (i.e., (MeAlO) 2 , 7; MeAl(OAlMe 2 ) 2 , cyclic 5). Significantly, our work demonstrates that intramolecular O→Al dative bonding results in cyclic isomers of MAO species (i.e., cyclic 5) with high oxophilicities. The stabilities of the [L(R 2 )FeCl ax (MAO) eq ] + species demonstrate that 5 provides for the ligating benefits of the cyclic MAO species 4 without the thermodynamically costly elimination of TMA. Mechanistic implications are discussed for the involvement of such Fe−O−Al bridged catalyst in olefin polymerization.

Original language	American English
Journal	Catalysts
Volume	12
DOIs	https://doi.org/10.3390/catal12030312
State	Published - Mar 1 2022

Keywords

Iron Pre‐catalyst
Methylaluminoxane (MAO)
Molecular Modeling
Olefin Polymerization
Oxophilicity
Pre‐catalyst MAO Adduct

Disciplines

Chemistry

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Transition Metal Catalyzed and MAO Assisted Olefin PolymerizationFinal published version, 2.01 MBLicense: CC BY

https://doi.org/10.3390/catal12030312

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@article{eabcf7e41f724a0e981d3c07e08605f4,

title = "Transition Metal‐Catalyzed and MAO‐Assisted Olefin Polymerization. Cyclic Isomers of Sinn{\textquoteright}s Dimer Are Excellent Ligands in Iron Complexes and Great Methylating Reagents",

abstract = " Methylaluminoxane (MAO) is the most commonly used co\&hyphen;catalyst for transition metalcatalyzed olefin polymerization, but the structures of MAO species and their catalytic functions remain topics of intensive study. We are interested in MAO\&hyphen;assisted polymerization with catalysts L(R 2 )FeCl 2 (L = tridentate pyridine\&hyphen;2,6\&hyphen;diyldimethanimine; imine\&hyphen;R = Me, Ph). It is our hypothesis that the MAO species is not merely enabling Fe\−Me bond formation but functions as an integral part of the active catalyst, a MAO adduct of the Fe\&hyphen;precatalyst [L(R 2 )FeCl] + . In this paper, we explored the possible structures of acyclic and cyclic MAO species and their complexation with pre\&hyphen;catalysts [L(R 2 )FeCl] + using quantum chemical approaches (MP2 and DFT). We report absolute and relative oxophilicities associated with the Fe\←O(MAO) adduct formation and provide compelling evidence that oxygen of an acyclic MAO species (i.e., O(AlMe 2 ) 2 , 4) cannot compete with the O\&hyphen;donor in cyclic MAO species (i.e., (MeAlO) 2 , 7; MeAl(OAlMe 2 ) 2 , cyclic 5). Significantly, our work demonstrates that intramolecular O\→Al dative bonding results in cyclic isomers of MAO species (i.e., cyclic 5) with high oxophilicities. The stabilities of the [L(R 2 )FeCl ax (MAO) eq ] + species demonstrate that 5 provides for the ligating benefits of the cyclic MAO species 4 without the thermodynamically costly elimination of TMA. Mechanistic implications are discussed for the involvement of such Fe\−O\−Al bridged catalyst in olefin polymerization.",

keywords = "Iron Pre‐catalyst, Methylaluminoxane (MAO), Molecular Modeling, Olefin Polymerization, Oxophilicity, Pre‐catalyst MAO Adduct",

author = "Kaidi Yang and Rainer Glaser",

year = "2022",

month = mar,

day = "1",

doi = "10.3390/catal12030312",

language = "American English",

volume = "12",

journal = "Catalysts",

issn = "2073-4344",

}

TY - JOUR

T1 - Transition Metal‐Catalyzed and MAO‐Assisted Olefin Polymerization. Cyclic Isomers of Sinn’s Dimer Are Excellent Ligands in Iron Complexes and Great Methylating Reagents

AU - Yang, Kaidi

AU - Glaser, Rainer

PY - 2022/3/1

Y1 - 2022/3/1

N2 - Methylaluminoxane (MAO) is the most commonly used co&hyphen;catalyst for transition metalcatalyzed olefin polymerization, but the structures of MAO species and their catalytic functions remain topics of intensive study. We are interested in MAO&hyphen;assisted polymerization with catalysts L(R 2 )FeCl 2 (L = tridentate pyridine&hyphen;2,6&hyphen;diyldimethanimine; imine&hyphen;R = Me, Ph). It is our hypothesis that the MAO species is not merely enabling Fe−Me bond formation but functions as an integral part of the active catalyst, a MAO adduct of the Fe&hyphen;precatalyst [L(R 2 )FeCl] + . In this paper, we explored the possible structures of acyclic and cyclic MAO species and their complexation with pre&hyphen;catalysts [L(R 2 )FeCl] + using quantum chemical approaches (MP2 and DFT). We report absolute and relative oxophilicities associated with the Fe←O(MAO) adduct formation and provide compelling evidence that oxygen of an acyclic MAO species (i.e., O(AlMe 2 ) 2 , 4) cannot compete with the O&hyphen;donor in cyclic MAO species (i.e., (MeAlO) 2 , 7; MeAl(OAlMe 2 ) 2 , cyclic 5). Significantly, our work demonstrates that intramolecular O→Al dative bonding results in cyclic isomers of MAO species (i.e., cyclic 5) with high oxophilicities. The stabilities of the [L(R 2 )FeCl ax (MAO) eq ] + species demonstrate that 5 provides for the ligating benefits of the cyclic MAO species 4 without the thermodynamically costly elimination of TMA. Mechanistic implications are discussed for the involvement of such Fe−O−Al bridged catalyst in olefin polymerization.

AB - Methylaluminoxane (MAO) is the most commonly used co&hyphen;catalyst for transition metalcatalyzed olefin polymerization, but the structures of MAO species and their catalytic functions remain topics of intensive study. We are interested in MAO&hyphen;assisted polymerization with catalysts L(R 2 )FeCl 2 (L = tridentate pyridine&hyphen;2,6&hyphen;diyldimethanimine; imine&hyphen;R = Me, Ph). It is our hypothesis that the MAO species is not merely enabling Fe−Me bond formation but functions as an integral part of the active catalyst, a MAO adduct of the Fe&hyphen;precatalyst [L(R 2 )FeCl] + . In this paper, we explored the possible structures of acyclic and cyclic MAO species and their complexation with pre&hyphen;catalysts [L(R 2 )FeCl] + using quantum chemical approaches (MP2 and DFT). We report absolute and relative oxophilicities associated with the Fe←O(MAO) adduct formation and provide compelling evidence that oxygen of an acyclic MAO species (i.e., O(AlMe 2 ) 2 , 4) cannot compete with the O&hyphen;donor in cyclic MAO species (i.e., (MeAlO) 2 , 7; MeAl(OAlMe 2 ) 2 , cyclic 5). Significantly, our work demonstrates that intramolecular O→Al dative bonding results in cyclic isomers of MAO species (i.e., cyclic 5) with high oxophilicities. The stabilities of the [L(R 2 )FeCl ax (MAO) eq ] + species demonstrate that 5 provides for the ligating benefits of the cyclic MAO species 4 without the thermodynamically costly elimination of TMA. Mechanistic implications are discussed for the involvement of such Fe−O−Al bridged catalyst in olefin polymerization.

KW - Iron Pre‐catalyst

KW - Methylaluminoxane (MAO)

KW - Molecular Modeling

KW - Olefin Polymerization

KW - Oxophilicity

KW - Pre‐catalyst MAO Adduct

UR - https://scholarsmine.mst.edu/chem_facwork/3160

UR - https://doi.org/10.3390/catal12030312

U2 - 10.3390/catal12030312

DO - 10.3390/catal12030312

M3 - Article

SN - 2073-4344

VL - 12

JO - Catalysts

JF - Catalysts

ER -

Transition Metal‐Catalyzed and MAO‐Assisted Olefin Polymerization. Cyclic Isomers of Sinn’s Dimer Are Excellent Ligands in Iron Complexes and Great Methylating Reagents

Abstract

Keywords

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