# Post-metallocene catalyst

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Catalyst for the industrial production of plastics

A **post-metallocene catalyst** is a kind of catalyst for the [polymerization](/source/Polymerization) of [olefins](/source/Olefin), i.e., the industrial production of some of the most common plastics. "Post-metallocene" refers to a class of homogeneous catalysts that are not [metallocenes](/source/Metallocene). This area has attracted much attention because the market for polyethylene, polypropylene, and related [copolymers](/source/Copolymer) is large. There is a corresponding intense market for new processes as indicated by the fact that, in the US alone, 50,000 patents were issued between 1991-2007 on polyethylene and polypropylene.[1]

Many methods exist to polymerize alkenes, including the traditional routes using [Philips catalyst](/source/Philips_catalyst) and traditional heterogeneous [Ziegler-Natta catalysts](/source/Ziegler-Natta_catalysts), which still are used to produce the bulk of polyethylene.

## Catalysts based on early transition metals

	- Early metal post-metallocene catalyst designs

		- Generic structure of a post-metallocene catalyst based on Dow's pyridyl-amido design.

		- Early examples of postmetallocene catalysts included [Schiff base](/source/Schiff_base) ligands.

Homogeneous metallocene catalysts, e.g., derived from or related to [zirconocene dichloride](/source/Zirconocene_dichloride) introduced a level of microstructural control that was unavailable with heterogeneous systems.[2] Metallocene catalysts are [homogeneous](https://en.wiktionary.org/wiki/Homogeneous) single-site systems, implying that a uniform catalyst is present in the solution. In contrast, commercially important Ziegler-Natta heterogeneous catalysts contain a distribution of catalytic sites. The catalytic properties of single-site catalysts can be controlled by modification of the ligand. Initially ligand modifications focused on various cyclopentadienyl derivatives, but great diversity was uncovered through high throughput screening. These post-metallocene catalysts employ a range of chelating ligands, often including [pyridine](/source/Pyridine) and amido (R2N−). These ligands are available in great diversity with respect to their steric and electronic properties. Such postmetallocene catalysts enabled the introduction of [Chain shuttling polymerization](/source/Chain_shuttling_polymerization).[1]

## Catalysts based on late transition metals

The copolymerization of ethylene with polar monomers has been heavily studied. The high [oxophilicity](/source/Oxophilic) of the early metals precluded their use in this application.[3]

	- Late metal post-metallocene catalyst designs

		- Catalyst supported by charge-neutral alpha-diimine ligands.

		- Catalyst supported by highly electron-withdrawing substituted ligand.[4]

		- Catalyst supported by anionic [Schiff base](/source/Schiff_base) ligand

		- Catalysts supported by tridentate [diiminopyridine](/source/Diiminopyridine) ligand.

Efforts to copolymerize polar comonomers led to catalysts based upon [nickel](/source/Nickel) and [palladium](/source/Palladium), inspired by the success of the [Shell Higher Olefin Process](/source/Shell_Higher_Olefin_Process). Typical post-metallocene catalysts feature bulky, neutral, alpha-[diimine](/source/Diimine) ligands.[3] DuPont commercialized the Versipol olefin polymerization system.[5] Eastman commercialized the related Gavilan technology.[6] These complexes catalyze the homopolymerize [ethylene](/source/Ethylene) to a variety of structures that range from high density [polyethylene](/source/Polyethylene) through hydrocarbon [plastomers](/source/Plastomer) and [elastomers](/source/Elastomers) by a mechanism referred to as “[chain-walking](/source/Chain-walking)”. By modifying the bulk of the [alpha-diimine](https://en.wikipedia.org/w/index.php?title=Alpha-diimine&action=edit&redlink=1), the product distribution of these systems can be 'tuned' to consist of hydrocarbon oils ([alpha-olefins](/source/Alpha-olefin)), similar to those produced by more tradition nickel(II) oligo/polymerization catalysts. As opposed to [metallocenes](/source/Metallocene), they can also randomly copolymerize ethylene with polar comonomers such as [methyl acrylate](/source/Methyl_acrylate).

A second class of catalysts feature mono-anionic bidentate ligands related to [salen ligands](/source/Salen_ligand).[7] and DuPont.[8][9]

The concept of bulky bis-imine ligands was extended to iron complexes[3] Representative catalysts feature [diiminopyridine](/source/Diiminopyridine) ligands. These catalysts are highly active but do not promote [chain walking](/source/Chain_walking). The give very linear high-density polyethylene when bulky and when the steric bulk is removed, they are very active for ethylene oligomerization to linear alpha-olefins.[3]

A salicylimine catalyst system based on zirconium exhibits high activity for [ethylene](/source/Ethylene) polymerization.[10] The catalysts can also produce some novel [polypropylene](/source/Polypropylene) structures.[11] Despite intensive efforts, few catalysts have been successfully commercialized for the copolymerization of polar monomers.

## References

1. ^ [***a***](#cite_ref-Chum_1-0) [***b***](#cite_ref-Chum_1-1) Chum, P. S.; Swogger, K. W., "Olefin Polymer Technologies-History and Recent Progress at the Dow Chemical Company", Progress in Polymer Science 2008, volume 33, 797-819. [doi](/source/Doi_(identifier)):[10.1016/j.progpolymsci.2008.05.003](https://doi.org/10.1016%2Fj.progpolymsci.2008.05.003)

1. **[^](#cite_ref-2)** Brintzinger, H. H.; Fischer, D.; Muelhaupt, R.; Rieger, B.; Waymouth, R. M., "Stereospecific Olefin Polymerization with Chiral Metallocene Catalysts", Angew. Chem. Int. Ed. Engl. 1995, 34, 1143-1170. [doi](/source/Doi_(identifier)):[10.1002/anie.199511431](https://doi.org/10.1002%2Fanie.199511431)

1. ^ [***a***](#cite_ref-Domski_3-0) [***b***](#cite_ref-Domski_3-1) [***c***](#cite_ref-Domski_3-2) [***d***](#cite_ref-Domski_3-3) Domski, G. J., Rose, J. M., Coates, G. W., Bolig, A. D., Brookhart, M., "Living alkene polymerization: New methods for the precision synthesis of polyolefins", Prog. Polymer Sci. 2007, volume 32, p.30. [doi](/source/Doi_(identifier)):[10.1016/j.progpolymsci.2006.11.001](https://doi.org/10.1016%2Fj.progpolymsci.2006.11.001)

1. **[^](#cite_ref-4)** Janeta, Mateusz; Heidlas, Julius X.; Daugulis, Olafs; Brookhart, Maurice (2021). ["2,4,6-Triphenylpyridinium: A Bulky, Highly Electron-Withdrawing Substituent That Enhances Properties of Nickel(II) Ethylene Polymerization Catalysts"](https://onlinelibrary.wiley.com/doi/abs/10.1002/anie.202013854). *Angewandte Chemie International Edition*. **60** (9): 4566–4569. [doi](/source/Doi_(identifier)):[10.1002/anie.202013854](https://doi.org/10.1002%2Fanie.202013854). [ISSN](/source/ISSN_(identifier)) [1521-3773](https://search.worldcat.org/issn/1521-3773). [OSTI](/source/OSTI_(identifier)) [1755772](https://www.osti.gov/biblio/1755772). [PMID](/source/PMID_(identifier)) [33230900](https://pubmed.ncbi.nlm.nih.gov/33230900). [S2CID](/source/S2CID_(identifier)) [227159941](https://api.semanticscholar.org/CorpusID:227159941).

1. **[^](#cite_ref-5)** US 5,866,663 "Process of Polymerizing Olefins," Samuel David Arthur, Alison Margaret Anne Bennett, Maurice S. Brookhart, Edward Bryan Coughlin, Jerald Feldman, Steven Dale Ittel, Lynda Kaye Johnson, Christopher Moore Killian; Kristina Ann Kreutzer, Elizabeth Forrester McCord, Stephan James McLain, Anju Parthasarathy, Lin Wang, Zhen-Yu Yang; February 2, 1999. WO 9623010 A2 960801.

1. **[^](#cite_ref-6)** MacKenzie, P. B.; Moody, L. S.; Killian, C. M.; Ponasik, J. A.; McDevitt, J. P. WO Patent Application 9840374, Sept. 17, 1998 to Eastman, priority date Feb 24, 1998.

1. **[^](#cite_ref-7)** C. Wang, S. Friedrich, T. R. Younkin, R. T. Li, R. H. Grubbs, D. A. Bansleben, M. W. Day, *[Organometallics](/source/Organometallics)*, **17**, 3149 (1998).

1. **[^](#cite_ref-8)** US 6,174,975, “Polymerization of Olefins,” Lynda Kaye Johnson; Alison Margaret Anne Bennett, Lin Wang, Anju Parthasarathy, Elisabeth Hauptman, Robert D. Simpson, Jerald Feldman, Edward Bryan Coughlin, and Steven Dale Ittel. January 16, 2001.

1. **[^](#cite_ref-9)** Janeta, Mateusz; Heidlas, Julius X.; Daugulis, Olafs; Brookhart, Maurice (2021). ["2,4,6-Triphenylpyridinium: A Bulky, Highly Electron-Withdrawing Substituent That Enhances Properties of Nickel(II) Ethylene Polymerization Catalysts"](https://onlinelibrary.wiley.com/doi/abs/10.1002/anie.202013854). *Angewandte Chemie International Edition*. **60** (9): 4566–4569. [doi](/source/Doi_(identifier)):[10.1002/anie.202013854](https://doi.org/10.1002%2Fanie.202013854). [ISSN](/source/ISSN_(identifier)) [1521-3773](https://search.worldcat.org/issn/1521-3773). [OSTI](/source/OSTI_(identifier)) [1755772](https://www.osti.gov/biblio/1755772). [PMID](/source/PMID_(identifier)) [33230900](https://pubmed.ncbi.nlm.nih.gov/33230900). [S2CID](/source/S2CID_(identifier)) [227159941](https://api.semanticscholar.org/CorpusID:227159941).

1. **[^](#cite_ref-10)** S. Matsui, Y. Tohi, M. Mitani, J. Saito, H. Makio, H. Tanaka, M. Nitabaru, T. Nakano, T, Fujita, *Chem. Lett.*, 1065 (1999).

1. **[^](#cite_ref-11)** [Steven D. Ittel](/source/Steven_Ittel) and Lynda K. Johnson and [Maurice Brookhart](/source/Maurice_Brookhart), Late-Metal Catalysts for Ethylene Homo- and Copolymerization, Chem. Rev. 2000, 100, 1169-1203.

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Adapted from the Wikipedia article [Post-metallocene catalyst](https://en.wikipedia.org/wiki/Post-metallocene_catalyst) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Post-metallocene_catalyst?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.