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Luo L, Younker JM, Zabula AV. Structure of methylaluminoxane (MAO): Extractable [Al(CH 3) 2] + for precatalyst activation. Science 2024; 384:1424-1428. [PMID: 38935705 DOI: 10.1126/science.adm7305] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2023] [Accepted: 05/13/2024] [Indexed: 06/29/2024]
Abstract
Methylaluminoxane (MAO) is used as a precatalyst activator for million ton-scale production of commercial polyolefins, but its precise structure and associated activation mechanisms have been a fundamental research puzzle for more than 40 years. We report here the crystallographic characterization of an active MAO component, which reveals a discrete two-dimensional sheet cluster [Al33O26(CH3)47][Al(CH3)3]2 featuring two trimethylaluminum units, Al(CH3)3, coordinated to two unsaturated aluminum sites. Our structural data are consistent with the hypothesis that the active sites bear coordinated Al(CH3)3 and provide [Al(CH3)2]+ for precatalyst activation. Quantum chemical calculations revealed the most preferred sites for [Al(CH3)2]+ abstraction (a change in Gibbs free energy of 0.0 kilocalories per mole). Olefin polymerization tests on metallocenes activated with the crystallized MAO show higher activities than with the commercial MAO.
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Affiliation(s)
- Lubin Luo
- ExxonMobil Technology and Engineering Company, Baytown, TX 77520, USA
| | - Jarod M Younker
- ExxonMobil Technology and Engineering Company, Baytown, TX 77520, USA
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2
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Collins S, Linnolahti M. Cages versus Sheets: A Critical Comparison in the Size Range Expected for Methylaluminoxane (MAO). Chemphyschem 2023; 24:e202300342. [PMID: 37314040 DOI: 10.1002/cphc.202300342] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2023] [Revised: 06/14/2023] [Accepted: 06/14/2023] [Indexed: 06/15/2023]
Abstract
New cage models (MeAlO)n (Me3 Al)m (n=16, m=6 or 7) isomeric with previously reported sheet models for the principle activator found in hydrolytic MAO (h-MAO) are compared at M06-2X and MN15 levels of theory using density functional theory with respect to their thermodynamic stability. Reactivity of the neutrals or corresponding anions with formula [(MeAlO)16 (Me3 Al)6 Me]- towards chlorination, and loss of Me3 Al is explored while reactivity of the neutrals towards formation of contact- and outer-sphere ion pairs from Cp2 ZrMe2 and Cp2 ZrMeCl is examined. The results suggest on balance that a cage model for this activator is less consistent with experiment than an isomeric sheet model, although the latter are more stable based on free energy.
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Affiliation(s)
- Scott Collins
- Department of Chemistry, University of Eastern Finland, Joensuu Campus, Yliopistokatu 7, 80100, Joensuu, Finland
| | - Mikko Linnolahti
- Department of Chemistry, University of Eastern Finland, Joensuu Campus, Yliopistokatu 7, 80100, Joensuu, Finland
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Zhang M, Feng Y, Lou L, Zhang H, Wang J, Yang Y. Flow Toolkit for Measuring Reaction Enthalpy and Application to Highly Exothermic Synthesis of Alkylaluminoxanes. Org Process Res Dev 2022. [DOI: 10.1021/acs.oprd.2c00072] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Mengbo Zhang
- State Key Laboratory of Chemical Engineering, College of Chemical and Biological Engineering, Zhejiang University, Hangzhou 310027, P. R. China
| | - Yirong Feng
- State Key Laboratory of Chemical Engineering, College of Chemical and Biological Engineering, Zhejiang University, Hangzhou 310027, P. R. China
| | - Linjin Lou
- State Key Laboratory of Chemical Engineering, College of Chemical and Biological Engineering, Zhejiang University, Hangzhou 310027, P. R. China
| | - Haomiao Zhang
- State Key Laboratory of Chemical Engineering, College of Chemical and Biological Engineering, Zhejiang University, Hangzhou 310027, P. R. China
| | - Jingdai Wang
- State Key Laboratory of Chemical Engineering, College of Chemical and Biological Engineering, Zhejiang University, Hangzhou 310027, P. R. China
| | - Yongrong Yang
- State Key Laboratory of Chemical Engineering, College of Chemical and Biological Engineering, Zhejiang University, Hangzhou 310027, P. R. China
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Tyumkina TV, Islamov DN, Kovyazin PV, Parfenova LV. Chain and cluster models of methylaluminoxane as activators of zirconocene hydride, alkyl and metallacyclopropane intermediates in alkene transformations. MOLECULAR CATALYSIS 2021. [DOI: 10.1016/j.mcat.2021.111768] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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Joshi A, Collins S, Linnolahti M, Zijlstra HS, Liles E, McIndoe JS. Spectroscopic Studies of Synthetic Methylaluminoxane: Structure of Methylaluminoxane Activators. Chemistry 2021; 27:8753-8763. [PMID: 33780574 DOI: 10.1002/chem.202100271] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2021] [Indexed: 11/06/2022]
Abstract
Hydrolysis of trimethylaluminum (Me3 Al) in polar solvents can be monitored by electrospray ionization mass spectrometry (ESI-MS) using the donor additive octamethyltrisiloxane [(Me3 SiO)2 SiMe2 , OMTS]. Using hydrated salts, hydrolytic methylaluminoxane (h-MAO) features different anion distributions, depending on the conditions of synthesis, and different activator contents as measured by NMR spectroscopy. Non-hydrolytic MAO was prepared using trimethylboroxine. The properties of this material, which contains incorporated boron, differ significantly from h-MAO. In the case of MAO prepared by direct hydrolysis, oligomeric anions are observed to rapidly form, and then more slowly evolve into a mixture dominated by an anion with m/z 1375 with formula [(MeAlO)16 (Me3 Al)6 Me]- . Theoretical calculations predict that sheet structures with composition (MeAlO)n (Me3 Al)m are favoured over other motifs for MAO in the size range suggested by the ESI-MS experiments. A possible precursor to the m/z 1375 anion is a local minimum based on the free energy released upon hydrolysis of Me3 Al.
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Affiliation(s)
- Anuj Joshi
- Department of Chemistry, University of Victoria, 3800 Finnerty Road, Victoria, BC V8P 5C2, Canada
| | - Scott Collins
- C/o Department of Chemistry, University of Victoria, 3800 Finnerty Road, Victoria, BC V8P 5C2, Canada
| | - Mikko Linnolahti
- Department of Chemistry, University of Eastern Finland, Joensuu Campus, Yliopistokatu 7, 80100, Joensuu, Finland
| | - Harmen S Zijlstra
- Department of Chemistry, University of Victoria, 3800 Finnerty Road, Victoria, BC V8P 5C2, Canada
| | - Elena Liles
- Department of Chemistry, University of Victoria, 3800 Finnerty Road, Victoria, BC V8P 5C2, Canada
| | - J Scott McIndoe
- Department of Chemistry, University of Victoria, 3800 Finnerty Road, Victoria, BC V8P 5C2, Canada
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Joshi A, Zijlstra HS, Liles E, Concepcion C, Linnolahti M, McIndoe JS. Real-time analysis of methylalumoxane formation. Chem Sci 2020; 12:546-551. [PMID: 34163784 PMCID: PMC8178985 DOI: 10.1039/d0sc05075j] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Methylalumoxane (MAO), a perennially useful activator for olefin polymerization precatalysts, is famously intractable to structural elucidation, consisting as it does of a complex mixture of oligomers generated from hydrolysis of pyrophoric trimethylaluminum (TMA). Electrospray ionization mass spectrometry (ESI-MS) is capable of studying those oligomers that become charged during the activation process. We have exploited that ability to probe the synthesis of MAO in real time, starting less than a minute after the mixing of H2O and TMA and tracking the first half hour of reactivity. We find that the process does not involve an incremental build-up of oligomers; instead, oligomerization to species containing 12–15 aluminum atoms happens within a minute, with slower aggregation to higher molecular weight ions. The principal activated product of the benchtop synthesis is the same as that observed in industrial samples, namely [(MeAlO)16(Me3Al)6Me]−, and we have computationally located a new sheet structure for this ion 94 kJ mol−1 lower in Gibbs free energy than any previously calculated. The activator methylaluminoxane is made by hydrolysis of trimethylaluminum. Analysis using ESI-MS reveals rapid formation of small oligomers is followed by slower aggregation to the larger precursors most capable of releasing [Me2Al]+.![]()
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Affiliation(s)
- Anuj Joshi
- Department of Chemistry, University of Victoria PO Box 1700 STN CSC, Victoria BC V8W 2Y2 Canada
| | - Harmen S Zijlstra
- Department of Chemistry, University of Victoria PO Box 1700 STN CSC, Victoria BC V8W 2Y2 Canada
| | - Elena Liles
- Department of Chemistry, University of Victoria PO Box 1700 STN CSC, Victoria BC V8W 2Y2 Canada
| | - Carina Concepcion
- Department of Chemistry, University of Victoria PO Box 1700 STN CSC, Victoria BC V8W 2Y2 Canada
| | - Mikko Linnolahti
- Department of Chemistry, University of Eastern Finland P.O. Box 111 FI-80101 Joensuu Finland
| | - J Scott McIndoe
- Department of Chemistry, University of Victoria PO Box 1700 STN CSC, Victoria BC V8W 2Y2 Canada
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Zaccaria F, Sian L, Zuccaccia C, Macchioni A. Ion pairing in transition metal catalyzed olefin polymerization. ADVANCES IN ORGANOMETALLIC CHEMISTRY 2020. [DOI: 10.1016/bs.adomc.2019.08.001] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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Zijlstra HS, Joshi A, Linnolahti M, Collins S, McIndoe JS. Interaction of Neutral Donors with Methylaluminoxane. Eur J Inorg Chem 2019. [DOI: 10.1002/ejic.201900153] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Harmen S. Zijlstra
- Department of Chemistry; University of Victoria; P. O. Box 3065 Victoria BC V8W3V6 Canada
| | - Anuj Joshi
- Department of Chemistry; University of Victoria; P. O. Box 3065 Victoria BC V8W3V6 Canada
| | - Mikko Linnolahti
- Department of Chemistry; University of Eastern Finland; P. O. Box 111 80101 Joensuu Finland
| | - Scott Collins
- Department of Chemistry; University of Victoria; P. O. Box 3065 Victoria BC V8W3V6 Canada
| | - J. Scott McIndoe
- Department of Chemistry; University of Victoria; P. O. Box 3065 Victoria BC V8W3V6 Canada
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Zaccaria F, Zuccaccia C, Cipullo R, Budzelaar PHM, Macchioni A, Busico V, Ehm C. BHT-Modified MAO: Cage Size Estimation, Chemical Counting of Strongly Acidic Al Sites, and Activation of a Ti-Phosphinimide Precatalyst. ACS Catal 2019. [DOI: 10.1021/acscatal.9b00076] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Francesco Zaccaria
- Dipartimento di Scienze Chimiche, Università di Napoli Federico II, Via Cintia, 80126 Napoli, Italy
- Dipartimento di Chimica, Biologia e Biotecnologie and CIRCC, Università di Perugia, Via Elce di Sotto 8, 06123 Perugia, Italy
| | - Cristiano Zuccaccia
- Dipartimento di Chimica, Biologia e Biotecnologie and CIRCC, Università di Perugia, Via Elce di Sotto 8, 06123 Perugia, Italy
| | - Roberta Cipullo
- Dipartimento di Scienze Chimiche, Università di Napoli Federico II, Via Cintia, 80126 Napoli, Italy
| | - Peter H. M. Budzelaar
- Dipartimento di Scienze Chimiche, Università di Napoli Federico II, Via Cintia, 80126 Napoli, Italy
| | - Alceo Macchioni
- Dipartimento di Chimica, Biologia e Biotecnologie and CIRCC, Università di Perugia, Via Elce di Sotto 8, 06123 Perugia, Italy
| | - Vincenzo Busico
- Dipartimento di Scienze Chimiche, Università di Napoli Federico II, Via Cintia, 80126 Napoli, Italy
| | - Christian Ehm
- Dipartimento di Scienze Chimiche, Università di Napoli Federico II, Via Cintia, 80126 Napoli, Italy
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Parfenova LV, Kovyazin PV, Tyumkina TV, Islamov DN, Lyapina AR, Karchevsky SG, Ivchenko PV. Reactions of bimetallic Zr,Al- hydride complexes with methylaluminoxane: NMR and DFT study. J Organomet Chem 2017. [DOI: 10.1016/j.jorganchem.2017.09.012] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Zijlstra HS, Linnolahti M, Collins S, McIndoe JS. Additive and Aging Effects on Methylalumoxane Oligomers. Organometallics 2017. [DOI: 10.1021/acs.organomet.7b00153] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Harmen S. Zijlstra
- Department
of Chemistry, University of Victoria, P.O. Box 3065, Victoria, British Columbia V8W 3V6, Canada
| | - Mikko Linnolahti
- Department
of Chemistry, University of Eastern Finland, P.O. Box 111, FI-80101 Joensuu, Finland
| | - Scott Collins
- Department
of Chemistry, University of Victoria, P.O. Box 3065, Victoria, British Columbia V8W 3V6, Canada
| | - J. Scott McIndoe
- Department
of Chemistry, University of Victoria, P.O. Box 3065, Victoria, British Columbia V8W 3V6, Canada
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Redzic E, Garoff T, Mardare CC, List M, Hesser G, Mayrhofer L, Hassel AW, Paulik C. Heterogeneous Ziegler–Natta catalysts with various sizes of MgCl2 crystallites: synthesis and characterization. IRANIAN POLYMER JOURNAL 2016. [DOI: 10.1007/s13726-016-0424-x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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