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dc.contributor.authorRünzi, Thomas
dc.contributor.authorTritschler, Ulrich
dc.contributor.authorRoesle, Philipp
dc.contributor.authorGöttker-Schnetmann, Inigo J.
dc.contributor.authorMöller, Heiko Maa
dc.contributor.authorCaporaso, Lucia
dc.contributor.authorPoater, Albert
dc.contributor.authorCavallo, Luigi
dc.contributor.authorMecking, Stefan
dc.date.accessioned2015-08-03T10:38:48Z
dc.date.available2015-08-03T10:38:48Z
dc.date.issued2012-12-10
dc.identifier.issn02767333
dc.identifier.doi10.1021/om300969d
dc.identifier.urihttp://hdl.handle.net/10754/562455
dc.description.abstract13C-Labeled ethylene polymerization (pre)catalysts [κ2-(anisyl)2P,O]Pd(13CH3)(L) (1-13CH3-L) (L = pyridine, dmso) based on di(2-anisyl)phosphine benzenesulfonate were used to assess the degree of incorporation of 13CH3 groups into the formed polyethylenes. Polymerizations of variable reaction time reveal that ca. 60-85% of the 13C-label is found in the polymer after already 1 min polymerization time, which provides evidence that the pre-equilibration between the catalyst precursor 1-13CH3-L and the active species 1-13CH3-(ethylene) is fast with respect to chain growth. The fraction of 1-13CH3-L that initiates chain growth is likely higher than the 60-85% determined from the 13C-labeled polymer chain ends since (a) chain walking results in in-chain incorporation of the 13C-label, (b) irreversible catalyst deactivation by formation of saturated (and partially volatile) alkanes diminishes the amount of 13CH3 groups incorporated into the polymer, and (c) palladium-bound 13CH3 groups, and more general palladium-bound alkyl(polymeryl) chains, partially transfer to phosphorus by reductive elimination. NMR and ESI-MS analyses of thermolysis reactions of 1-13CH3-L provide evidence that a mixture of phosphonium salts (13CH3)xP+(aryl)4-x (2-7) is formed in the absence of ethylene. In addition, isolation and characterization of the mixed bis(chelate) palladium complex [κ2-(anisyl)2P,O]Pd[κ2-(anisyl) (13CH3)P,O] (11) by NMR and X-ray diffraction analyses from these mixtures indicate that oxidative addition of phosphonium salts to palladium(0) species is also operative. The scrambling of palladium-bound carbyls and phosphorus-bound aryls is also relevant under NMR, as well as preparative reactor polymerization conditions exemplified by the X-ray diffraction analysis of [κ2-(anisyl)2P,O] Pd[κ2-(anisyl)(CH2CH3)P,O] (12) and [κ2-(anisyl)2P,O]Pd[κ2-(anisyl) ((CH2)3CH3)P,O] (13) isolated from pressure reactor polymerization experiments. In addition, ESI-MS analyses of reactor polymerization filtrates indicate the presence of (odd- and even-numbered alkyl)(anisyl)phosphine sulfonates (14) and their respective phosphine oxides (15). Furthermore, 2-(vinyl)anisole was detected in NMR tube and reactor polymerizations, which results from ethylene insertion into a palladium-anisyl bond and concomitant β-hydride elimination. In addition to these scrambling reactions, formation of alkanes or fully saturated polymer chains, bis(chelate)palladium complexes [κ2-P,O]2Pd, and palladium black was identified as an irreversible catalyst deactivation pathway. This deactivation proceeds by reaction of palladium alkyl complexes with palladium hydride complexes [κ2-P,O]Pd(H)(L) or by reaction with the free ligand H[P,O] generated by reductive elimination from [κ2-P,O]Pd(H)(L). The model hydride complex 1-H-P tBu3 has been synthesized in order to establish whether 1-H-PtBu3 or H[P,O] is responsible for the irreversible catalyst deactivation. However, upon reaction with 1-(13)CH 3-L or 1-CH2CH3-PPh3, both 1-H-PtBu3 and H[P,O] result in formation of methane or ethane, even though H[P,O] reacts faster than 1-H-PtBu3. DFT calculations show that reductive elimination to form H[P,O] and (alkyl)[P,O] from 1-H/(alkyl)-PtBu3 is kinetically accessible, as is the oxidative readdition of the P-H bond of H[P,O] and the P-anisyl bond of (alkyl)[P,O] to [Pd(PtBu3)2]. These calculations also indicate that for a reaction sequence comprising reductive elimination of H[P,O] from 1-H-PtBu3 and reaction of H[P,O] with 1-CH3-PtBu3, 1-CH3-dmso, or 1-CH2CH3-PPh3 to form methane or ethane, the rate-limiting step is reductive elimination of H[P,O] with a barrier of 124 kJ mol-1. However, a second reaction coordinate was found for the reaction of 1-H-PtBu3 with 1-CH3-P tBu3 or 1-CH3-dmso, which evolves into bimetallic transition-state geometries with a nearly linear H-(CH 3)-Pd alignment and which exhibits a barrier of 131 or 95 kJ mol -1 for the formation of methane. © 2012 American Chemical Society.
dc.description.sponsorshipFinancial support by the DFG (Me1388/10-1) is gratefully acknowledged. P.R. thanks the Carl Zeiss Foundation for a research stipend. The authors thank the HPC team of ENEA (www.enea.it) for using the ENEA.-GRID and the HPC facilities CRESCO (www.cresco.enea.it) in Portici, Italy.
dc.publisherAmerican Chemical Society (ACS)
dc.titleActivation and deactivation of neutral palladium(II) phosphinesulfonato polymerization catalysts
dc.typeArticle
dc.contributor.departmentBiological and Environmental Sciences and Engineering (BESE) Division
dc.contributor.departmentKAUST Catalysis Center (KCC)
dc.contributor.departmentPhysical Sciences and Engineering (PSE) Division
dc.contributor.departmentChemical Science Program
dc.identifier.journalOrganometallics
dc.contributor.institutionDepartment of Chemistry, University of Konstanz, 78464 Konstanz, Germany
dc.contributor.institutionDepartment of Chemistry, University of Salerno, Via Ponte Don Melillo, 84084-Fisciano (SA), Italy
dc.contributor.institutionInstitut de Química Computacional, Department de Química, Campus de Montilivi, E-17071 Girona, Spain
kaust.personCavallo, Luigi
dc.relation.isSupplementedByRünzi, T., Tritschler, U., Roesle, P., Göttker-Schnetmann, I., Möller, H. M., Caporaso, L., … Mecking, S. (2013). CCDC 897155: Experimental Crystal Structure Determination [Data set]. Cambridge Crystallographic Data Centre. https://doi.org/10.5517/ccz3kh3
dc.relation.isSupplementedByDOI:10.5517/ccz3kh3
dc.relation.isSupplementedByHANDLE:http://hdl.handle.net/10754/624744
dc.relation.isSupplementedByRünzi, T., Tritschler, U., Roesle, P., Göttker-Schnetmann, I., Möller, H. M., Caporaso, L., … Mecking, S. (2013). CCDC 897156: Experimental Crystal Structure Determination [Data set]. Cambridge Crystallographic Data Centre. https://doi.org/10.5517/ccz3kj4
dc.relation.isSupplementedByDOI:10.5517/ccz3kj4
dc.relation.isSupplementedByHANDLE:http://hdl.handle.net/10754/624745
dc.relation.isSupplementedByRünzi, T., Tritschler, U., Roesle, P., Göttker-Schnetmann, I., Möller, H. M., Caporaso, L., … Mecking, S. (2013). CCDC 897157: Experimental Crystal Structure Determination [Data set]. Cambridge Crystallographic Data Centre. https://doi.org/10.5517/ccz3kk5
dc.relation.isSupplementedByDOI:10.5517/ccz3kk5
dc.relation.isSupplementedByHANDLE:http://hdl.handle.net/10754/624746
dc.relation.isSupplementedByRünzi, T., Tritschler, U., Roesle, P., Göttker-Schnetmann, I., Möller, H. M., Caporaso, L., … Mecking, S. (2013). CCDC 897158: Experimental Crystal Structure Determination [Data set]. Cambridge Crystallographic Data Centre. https://doi.org/10.5517/ccz3kl6
dc.relation.isSupplementedByDOI:10.5517/ccz3kl6
dc.relation.isSupplementedByHANDLE:http://hdl.handle.net/10754/624747


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