Olefin polymerization on Cr(III)/SiO2: Mechanistic insights from the differences in reactivity between ethene and propene
Silica-supported well-defined Cr(III) sites, which polymerize ethene, are barely reactive towards propene while they copolymerize propene and ethene, a reactivity pattern similar to what is observed for the Phillips catalyst. In contrast to ethene, propene is only polymerized in low amounts and by a...
- Autores:
- Tipo de recurso:
- Fecha de publicación:
- 2017
- Institución:
- Universidad de Medellín
- Repositorio:
- Repositorio UDEM
- Idioma:
- eng
- OAI Identifier:
- oai:repository.udem.edu.co:11407/4257
- Acceso en línea:
- http://hdl.handle.net/11407/4257
- Palabra clave:
- Amorphous model
CrIII sites
DFT calculations
Ethene polymerization
Propene polymerization
Silica
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- License
- http://purl.org/coar/access_right/c_16ec
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| dc.title.spa.fl_str_mv |
Olefin polymerization on Cr(III)/SiO2: Mechanistic insights from the differences in reactivity between ethene and propene |
| title |
Olefin polymerization on Cr(III)/SiO2: Mechanistic insights from the differences in reactivity between ethene and propene |
| spellingShingle |
Olefin polymerization on Cr(III)/SiO2: Mechanistic insights from the differences in reactivity between ethene and propene Amorphous model CrIII sites DFT calculations Ethene polymerization Propene polymerization Silica |
| title_short |
Olefin polymerization on Cr(III)/SiO2: Mechanistic insights from the differences in reactivity between ethene and propene |
| title_full |
Olefin polymerization on Cr(III)/SiO2: Mechanistic insights from the differences in reactivity between ethene and propene |
| title_fullStr |
Olefin polymerization on Cr(III)/SiO2: Mechanistic insights from the differences in reactivity between ethene and propene |
| title_full_unstemmed |
Olefin polymerization on Cr(III)/SiO2: Mechanistic insights from the differences in reactivity between ethene and propene |
| title_sort |
Olefin polymerization on Cr(III)/SiO2: Mechanistic insights from the differences in reactivity between ethene and propene |
| dc.contributor.affiliation.spa.fl_str_mv |
Delley, M.F., ETH Zürich, Department of Chemistry and Applied Biosciences, Vladimir-Prelog-Weg 1-5, Zürich, Switzerland Praveen, C.S., ETH Zürich, Department of Chemistry and Applied Biosciences, Vladimir-Prelog-Weg 1-5, Zürich, Switzerland Borosy, A.P., ETH Zürich, Department of Chemistry and Applied Biosciences, Vladimir-Prelog-Weg 1-5, Zürich, Switzerland Núñez-Zarur, F., ETH Zürich, Department of Chemistry and Applied Biosciences, Vladimir-Prelog-Weg 1-5, Zürich, Switzerland, Facultad de Facultad de Ciencias Básicas, Universidad de Medellín, Carrera 87 N° 30-65, Medellín, Colombia Comas-Vives, A., ETH Zürich, Department of Chemistry and Applied Biosciences, Vladimir-Prelog-Weg 1-5, Zürich, Switzerland Copéret, C., ETH Zürich, Department of Chemistry and Applied Biosciences, Vladimir-Prelog-Weg 1-5, Zürich, Switzerland |
| dc.subject.keyword.eng.fl_str_mv |
Amorphous model CrIII sites DFT calculations Ethene polymerization Propene polymerization Silica |
| topic |
Amorphous model CrIII sites DFT calculations Ethene polymerization Propene polymerization Silica |
| description |
Silica-supported well-defined Cr(III) sites, which polymerize ethene, are barely reactive towards propene while they copolymerize propene and ethene, a reactivity pattern similar to what is observed for the Phillips catalyst. In contrast to ethene, propene is only polymerized in low amounts and by a small fraction of sites, while during propene/ethene copolymerization small amounts of olefinic oligomers are formed. This difference of reactivity pattern among various olefins is further examined by DFT calculations using periodic amorphous models, focusing on the initiation of polymerization by olefin insertion into the Cr–O bond vs. the heterolytic C–H activation of the alkene. For both mechanisms, we found that the initial activation displays similar energetics for propene and ethene, while the subsequent propene insertion associated with chain growth becomes rather demanding, which rationalizes the observed difference of reactivity between ethene and propene. © 2017 Elsevier Inc. |
| publishDate |
2017 |
| dc.date.accessioned.none.fl_str_mv |
2017-12-19T19:36:42Z |
| dc.date.available.none.fl_str_mv |
2017-12-19T19:36:42Z |
| dc.date.created.none.fl_str_mv |
2017 |
| dc.type.eng.fl_str_mv |
Article |
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http://purl.org/coar/version/c_970fb48d4fbd8a85 |
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http://purl.org/coar/resource_type/c_6501 http://purl.org/coar/resource_type/c_2df8fbb1 |
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info:eu-repo/semantics/article |
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219517 |
| dc.identifier.uri.none.fl_str_mv |
http://hdl.handle.net/11407/4257 |
| dc.identifier.doi.none.fl_str_mv |
10.1016/j.jcat.2017.08.016 |
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reponame:Repositorio Institucional Universidad de Medellín |
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instname:Universidad de Medellín |
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219517 10.1016/j.jcat.2017.08.016 reponame:Repositorio Institucional Universidad de Medellín instname:Universidad de Medellín |
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http://hdl.handle.net/11407/4257 |
| dc.language.iso.none.fl_str_mv |
eng |
| language |
eng |
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https://www.scopus.com/inward/record.uri?eid=2-s2.0-85029025032&doi=10.1016%2fj.jcat.2017.08.016&partnerID=40&md5=2f7fe65684e78b4b350d61d8c50ed0eb |
| dc.relation.ispartofes.spa.fl_str_mv |
Journal of Catalysis Journal of Catalysis Volume 354, 2017, Pages 223-230 |
| dc.relation.references.spa.fl_str_mv |
Ajjou, J. A. N., Scott, S. L., & Paquet, V. (1998). Synthesis and characterization of silica-stabilized chromium(IV) alkylidene complexes. Journal of the American Chemical Society, 120(2), 415-416. doi:10.1021/ja973177a Amor Nait Ajjou, J., & Scott, S. L. (1997). Reactions of tetraalkylchromium(IV) with silica: Mechanism of grafting and characterization of surface organometallic complexes. Organometallics, 16(1), 86-92. doi:10.1021/om960612l Arlman, E. J. (1964). Ziegler-natta catalysis II. surface structure of layer-lattice transition metal chlorides. Journal of Catalysis, 3(1), 89-98. Arlman, E. J., & Cossee, P. (1964). Ziegler-natta catalysis III. stereospecific polymerization of propene with the catalyst system TiCl3AlEt3. Journal of Catalysis, 3(1), 99-104. Beck, D. D., & Lunsford, J. H. (1981). The active site for ethylene polymerization over chromium supported on silica. Journal of Catalysis, 68(1), 121-131. doi:10.1016/0021-9517(81)90045-2 Braunschweig, H., & Breitling, F. M. (2006). Constrained geometry complexes-synthesis and applications. Coordination Chemistry Reviews, 250(21-22), 2691-2720. doi:10.1016/j.ccr.2005.10.022 Brintzinger, H. H., Fischer, D., Mülhaupt, R., Rieger, B., & Waymouth, R. M. (1995). Stereospecific olefin polymerization with chiral metallocene catalysts. Angewandte Chemie International Edition in English, 34(11), 1143-1170. doi:10.1002/anie.199511431 Brown, C., Krzystek, J., Achey, R., Lita, A., Fu, R., Meulenberg, R. W., . . . Scott, S. L. (2015). Mechanism of initiation in the phillips ethylene polymerization catalyst: Redox processes leading to the active site.ACS Catalysis, 5(9), 5574-5583. doi:10.1021/acscatal.5b00927 Broyden, C. G. (1970). The convergence of single rank quasi newton methods. Mathematics of Computation, 24(110), 365-382. doi:10.1090/S0025-5718-1970-0279993-0 Chakrabarti, A., Gierada, M., Handzlik, J., & Wachs, I. E. (2016). Operando molecular spectroscopy during ethylene polymerization by supported CrOx/SiO2 catalysts: Active sites, reaction intermediates, and structure-activity relationship. Topics in Catalysis, 59(8-9), 725-739. doi:10.1007/s11244-016-0546-6 Chen, E. Y. -., & Marks, T. J. (2000). Cocatalysts for metal-catalyzed olefin polymerization: Activators, activation processes, and structure-activity relationships. Chemical Reviews, 100(4), 1391-1434. doi:10.1021/cr980462j Cheng, R., Liu, Z., Zhong, L., He, X., Qiu, P., Terano, M., . . . Liu, B. (2013). Phillips Cr/silica catalyst for ethylene polymerization doi:10.1007/12-2013-222 Coates, G. W. (2000). Precise control of polyolefin stereochemistry using single-site metal catalysts. Chemical Reviews, 100(4), 1223-1252. doi:10.1021/cr990286u Coates, G. W., Hustad, P. D., & Reinartz, S. (2002). Catalysts for the living insertion polymerization of alkenes: Access to new polyolefin architectures using ziegler-natta chemistry. Angewandte Chemie - International Edition, 41(13), 2236-2257. doi:10.1002/1521-3773(20020703)41 Comas-Vives, A. (2016). Amorphous SiO2 surface models: Energetics of the dehydroxylation process, strain, ab initio atomistic thermodynamics and IR spectroscopic signatures. Physical Chemistry Chemical Physics, 18(10), 7475-7482. doi:10.1039/c6cp00602g Conley, M. P., Delley, M. F., Núnez-Zarur, F., Comas-Vives, A., & Copéret, C. (2015). Heterolytic activation of C-H bonds on CrIII-O surface sites is a key step in catalytic polymerization of ethylene and dehydrogenation of propane. Inorganic Chemistry, 54(11), 5065-5078. doi:10.1021/ic502696n Conley, M. P., Delley, M. F., Siddiqi, G., Lapadula, G., Norsic, S., Monteil, V., . . . Copéret, C. (2014). Polymerization of ethylene by silica-supported dinuclear CrIII sites through an initiation step involving C=H bond activation. Angewandte Chemie - International Edition, 53(7), 1872-1876. doi:10.1002/anie.201308983 Copéret, C., Chabanas, M., Petroff Saint-Arroman, R., & Basset, J. -. (2003). Surface organometallic chemistry: Homogeneous and heterogeneous catalysis: Bridging the gap through surface organometallic chemistry. Angewandte Chemie - International Edition, 42(2), 156-181. doi:10.1002/anie.200390072 Copéret, C., Comas-Vives, A., Conley, M. P., Estes, D. P., Fedorov, A., Mougel, V., . . . Zhizhko, P. A. (2016). Surface organometallic and coordination chemistry toward single-site heterogeneous catalysts: Strategies, methods, structures, and activities. Chemical Reviews, 116(2), 323-421. doi:10.1021/acs.chemrev.5b00373 Corradini, P., Guerra, G., & Cavallo, L. (2004). Do new century catalysts unravel the mechanism of stereocontrol of old ziegler-natta catalysts? Accounts of Chemical Research, 37(4), 231-241. doi:10.1021/ar030165n Cossee, P. (1964). Ziegler-natta catalysis I. mechanism of polymerization of α-olefins with ziegler-natta catalysts. Journal of Catalysis, 3(1), 80-88. Delley, M. F. (2015). A molecular approach to well-defined metal sites supported on oxides with oxidation state and nuclearity control. Chimia, 69(4), 168-171. doi:10.2533/chimia.2015.168 Delley, M. F., Lapadula, G., Núñez-Zarur, F., Comas-Vives, A., Kalendra, V., Jeschke, G., . . . Copéret, C. (2017). Local structures and heterogeneity of silica-supported M(III) sites evidenced by EPR, IR, NMR, and luminescence spectroscopies. Journal of the American Chemical Society, 139(26), 8855-8867. doi:10.1021/jacs.7b02179 Delley, M. F., Núñez-Zarur, F., Conley, M. P., Comas-Vives, A., Siddiqi, G., Norsic, S., . . . Copéret, C. (2014). Proton transfers are key elementary steps in ethylene polymerization on isolated chromium(III) silicates. Proceedings of the National Academy of Sciences of the United States of America, 111(32), 11624-11629. doi:10.1073/pnas.1405314111 Espelid, Ø., & Børve, K. J. (2002). Molecular-level insight into Cr/silica phillips-type catalysts: Polymerization-active dinuclear chromium sites. Journal of Catalysis, 206(2), 331-338. doi:10.1006/jcat.2001.3499 Floryan, L., Borosy, A. P., Núñez-Zarur, F., Comas-Vives, A., & Copéret, C. (2017). Strain effect and dual initiation pathway in CrIII/SiO2polymerization catalysts from amorphous periodic models. Journal of Catalysis, 346, 50-56. doi:10.1016/j.jcat.2016.11.037 Fong, A., Peters, B., & Scott, S. L. (2016). One-electron-redox activation of the reduced phillips polymerization catalyst, via alkylchromium(IV) homolysis: A computational assessment. ACS Catalysis, 6(9), 6073-6085. doi:10.1021/acscatal.6b01728 Fong, A., Yuan, Y., Ivry, S. L., Scott, S. L., & Peters, B. (2015). Computational kinetic discrimination of ethylene polymerization mechanisms for the phillips (Cr/SiO2) catalyst. ACS Catalysis, 5(6), 3360-3374. doi:10.1021/acscatal.5b00016 Fujdala, K. L., & Tilley, T. D. (2003). Design and synthesis of heterogeneous catalysts: The thermolytic molecular precursor approach. Journal of Catalysis, 216(1-2), 265-275. doi:10.1016/S0021-9517(02)00106-9 Ghiotti, G., Garrone, E., Coluccia, S., Morterra, C., & Zecchina, A. (1979). Evidence for alkylidenic configuration of polymethylene chains on a phillips catalyst. Journal of the Chemical Society, Chemical Communications, (22), 1032-1033. doi:10.1039/C39790001032 Ghiotti, G., Garrone, E., & Zecchina, A. (1988). IR investigation of polymerization centres of the phillips catalyst. Journal of Molecular Catalysis, 46(1-3), 61-77. doi:10.1016/0304-5102(88)85083-1 Gierada, M., & Handzlik, J. (2017). Active sites formation and their transformations during ethylene polymerization by the phillips CrOx/SiO2 catalyst. Journal of Catalysis, 352, 314-328. doi:10.1016/j.jcat.2017.05.025 Goedecker, S., Teter, M., & Hutter, J. (1996). Separable dual-space gaussian pseudopotentials. Physical Review B - Condensed Matter and Materials Physics, 54(3), 1703-1710. Grimme, S., Antony, J., Ehrlich, S., & Krieg, H. (2010). A consistent and accurate ab initio parametrization of density functional dispersion correction (DFT-D) for the 94 elements H-pu. Journal of Chemical Physics, 132(15) doi:10.1063/1.3382344 Grimme, S., Ehrlich, S., & Goerigk, L. (2011). Effect of the damping function in dispersion corrected density functional theory. Journal of Computational Chemistry, 32(7), 1456-1465. doi:10.1002/jcc.21759 Groppo, E., Estephane, J., Lamberti, C., Spoto, G., & Zecchina, A. (2007). Ethylene, propylene and ethylene oxide in situ polymerization on the cr(II)/SiO2 system: A temperature- and pressure-dependent investigation. Catalysis Today, 126(1-2), 228-234. doi:10.1016/j.cattod.2007.01.052 Groppo, E., Lamberti, C., Bordiga, S., Spoto, G., & Zecchina, A. (2006). In situ FTIR spectroscopy of key intermediates in the first stages of ethylene polymerization on the Cr/SiO2 phillips catalyst: Solving the puzzle of the initiation mechanism? Journal of Catalysis, 240(2), 172-181. doi:10.1016/j.jcat.2006.03.006 Groppo, E., Lamberti, C., Bordiga, S., Spoto, G., & Zecchina, A. (2005). The structure of active centers and the ethylene polymerization mechanism on the Cr/SiO2 catalyst: A frontier for the characterization methods. Chemical Reviews, 105(1), 115-183. doi:10.1021/cr040083s Grubbs, R. H., & Coates, G. W. (1996). Acc.Chem.Res., 29, 85-93. Hartwigsen, C., Goedecker, S., & Hutter, J. (1998). Relativistic separable dual-space gaussian pseudopotentials from H to rn. Physical Review B - Condensed Matter and Materials Physics, 58(7), 3641-3662. Ikeda, H., Monoi, T., & Sasaki, Y. (2003). Performance of the cr[CH(SiMe3)2]3/SiO2 catalyst for ethylene polymerization compared with the performance of the phillips catalyst. Journal of Polymer Science, Part A: Polymer Chemistry, 41(3), 413-419. doi:10.1002/pola.10590 Ittel, S. D., Johnson, L. K., & Brookhart, M. (2000). Late-metal catalysts for ethylene homo- and copolymerization. Chemical Reviews, 100(4), 1169-1203. doi:10.1021/cr9804644 Ivin, K. J., Rooney, J. J., Stewart, C. D., Green, M. L. H., & Mahtab, R. (1978). Mechanism for the stereospecific polymerization of olefins by ziegler-natta catalysts. Journal of the Chemical Society, Chemical Communications, (14), 604-606. doi:10.1039/C39780000604 Kakugo, M., Naito, Y., Mizunuma, K., & Miyatake, T. (1982). 13C NMR determination of monomer sequence distribution in ethylene-propylene copolymers prepared with δ-TiCl3Al(C2H5)2Cl. Macromolecules, 15(4), 1150-1152. doi:10.1021/ma00232a037 Kaminsky, W. (2012). Discovery of methylaluminoxane as cocatalyst for olefin polymerization. Macromolecules, 45(8), 3289-3297. doi:10.1021/ma202453u Kaminsky, W. (1998). Highly active metallocene catalysts for olefin polymerization. Journal of the Chemical Society - Dalton Transactions, (9), 1413-1418. Krack, M. (2005). Pseudopotentials for H to kr optimized for gradient-corrected exchange-correlation functionals. Theoretical Chemistry Accounts, 114(1-3), 145-152. doi:10.1007/s00214-005-0655-y Krauss, H. L., & Stach, H. (1969). Über oberflächenverbindungen von übergangsmetallen. IV. polymerisationsreaktionen an Oberflächen‐Chrom(II)‐Verbindungen. ZAAC ‐ Journal of Inorganic and General Chemistry, 366(5-6), 280-290. doi:10.1002/zaac.19693660505 Liu, B., Nakatani, H., & Terano, M. (2003). Mechanistic implications of the unprecedented transformations of ethene into propene and butene over phillips CrOx/SiO2 catalyst during induction period. Journal of Molecular Catalysis A: Chemical, 201(1-2), 189-197. doi:10.1016/S1381-1169(03)00151-1 Liu, D., & Nocedal, J. (1989). Siam.J.Sci.Stat.Comp., 10, 1-17. Liu, H. -., Cai, I. C., Fedorov, A., Ziegler, M. S., Copéret, C., & Tilley, T. D. (2016). Tricoordinate organochromium(III) complexes supported by a bulky silylamido ligand produce ultra-high-molecular weight polyethylene in the absence of activators. Helvetica Chimica Acta, 99(11), 859-867. doi:10.1002/hlca.201600199 Liu, Z., He, X., Cheng, R., Eisen, M. S., Terano, M., Scott, S. L., & Liu, B. (2014). Adv.Chem.Eng., 44, 127-191. MacAdams, L. A., Buffone, G. P., Incarvito, C. D., Rheingold, A. L., & Theopold, K. H. (2005). A chromium catalyst for the polymerization of ethylene as a homogeneous model for the phillips catalyst. Journal of the American Chemical Society, 127(4), 1082-1083. doi:10.1021/ja043877x Masson, P., Llauro-Darricades, M. -., Spitz, R., & Cheng, H. N. (1996). A study of the dispersity of catalytic sites in ethylene/propylene copolymerization through computer-assisted 13C NMR analysis.International Journal of Polymer Analysis and Characterization, 2(4), 379-393. McDaniel, M. P. (1985). Supported chromium catalysts for ethylene polymerization doi:10.1016/S0360-0564(08)60258-8 Myers, D. L., & Lunsford, J. H. (1985). Silica-supported chromium catalysts for ethylene polymerization. Journal of Catalysis, 92(2), 260-271. doi:10.1016/0021-9517(85)90260-X Nakamura, A., Ito, S., & Nozaki, K. (2009). Coordination-insertion copolymerization of fundamental polar monomers. Chemical Reviews, 109(11), 5215-5244. doi:10.1021/cr900079r Nocedal, J. (1980). Updating quasi-newton matrices with limited storage. Math.Comput., 35(151), 773-782. Novokshonova, L. A., & Zakharov, V. A. (2013). Kinetics of olefin polymerization and active sites of heterogeneous ziegler-natta catalysts doi:10.1007/12-2013-227 Núñez-Zarur, F., & Comas-Vives, A. (2015). The effect of the electronic nature of spectator ligands in the C-H bond activation of ethylene by cr(III) silicates: An ab initio study. Chimia, 69(4), 225-229. doi:10.2533/chimia.2015.225 Pelletier, J. D. A., & Basset, J. -. (2016). Catalysis by design: Well-defined single-site heterogeneous catalysts. Accounts of Chemical Research, 49(4), 664-677. doi:10.1021/acs.accounts.5b00518 Perdew, J. P., Burke, K., & Ernzerhof, M. (1996). Generalized gradient approximation made simple. Physical Review Letters, 77(18), 3865-3868. doi:10.1103/PhysRevLett.77.3865 Perdew, J. P., Ruzsinszky, A., Csonka, G. I., Vydrov, O. A., Scuseria, G. E., Constantin, L. A., . . . Burke, K. (2008). Restoring the density-gradient expansion for exchange in solids and surfaces. Physical Review Letters, 100(13) doi:10.1103/PhysRevLett.100.136406 Przhevalskaya, L. K., Shvets, V. A., & Kazansky, V. B. (1975). The study of active centers of ethylene polymerization over chromium catalysts prepared from tri- and bivalent chromium compounds. Journal of Catalysis, 39(3), 363-368. doi:10.1016/0021-9517(75)90302-4 Rappé, A. K., Skiff, W. M., & Casewit, C. J. (2000). Modeling metal-catalyzed olefin polymerization. Chemical Reviews, 100(4), 1435-1456. doi:10.1021/cr9902493 Rebenstorf, B. (1988). An IR study of the polymerization mechanism of the phillips catalyst. Journal of Molecular Catalysis, 45(2), 263-274. doi:10.1016/0304-5102(88)80016-6 Rebenstorf, B., & Larsson, R. (1981). Why do homogeneous analogs of phillips (CrO3/SiO2) and union carbide (Chromocene/SiO2) polyethylene catalysts fail? some answers from ir investigations. Journal of Molecular Catalysis, 11(2-3), 247-256. doi:10.1016/0304-5102(81)87012-5 Shanno, D. F., & Kettler, P. C. (1970). Optimal conditioning of quasi-newton methods. Mathematics of Computation, 24(111), 657-664. doi:10.1090/S0025-5718-1970-0274030-6 Stürzel, M., Mihan, S., & Mülhaupt, R. (2016). From multisite polymerization catalysis to sustainable materials and all-polyolefin composites. Chemical Reviews, 116(3), 1398-1433. doi:10.1021/acs.chemrev.5b00310 Tada, M., & Iwasawa, Y. (2007). Advanced design of catalytically active reaction space at surfaces for selective catalysis. Coordination Chemistry Reviews, 251(21-24), 2702-2716. doi:10.1016/j.ccr.2007.06.008 Theopold, K. H. (1998). Homogeneous chromium catalysts for olefin polymerization. European Journal of Inorganic Chemistry, (1), 15-24. Retrieved from www.scopus.com Thomas, B. J., Noh, S. K., Sendlinger, S. C., & Schulte, G. K. (1991). Paramagnetic alkylchromium compounds as homogeneous catalysts for the polymerization of ethylene. Journal of the American Chemical Society, 113(3), 893-902. doi:10.1021/ja00003a024 VandeVondele, J., & Hutter, J. (2003). An efficient orbital transformation method for electronic structure calculations. Journal of Chemical Physics, 118(10), 4365-4369. doi:10.1063/1.1543154 VandeVondele, J., & Hutter, J. (2007). Gaussian basis sets for accurate calculations on molecular systems in gas and condensed phases. Journal of Chemical Physics, 127(11) doi:10.1063/1.2770708 Weckhuysen, B. M., & Schoonheydt, R. A. (1999). Olefin polymerization over supported chromium oxide catalysts. Catalysis Today, 51(2), 215-221. Wegener, S. L., Marks, T. J., & Stair, P. C. (2012). Design strategies for the molecular level synthesis of supported catalysts. Accounts of Chemical Research, 45(2), 206-214. doi:10.1021/ar2001342 Weiss, K., & Krauss, H. -. (1984). Surface compounds of transition metals. XXVIII. polymerization of n-1-alkenes with surface chromium(II) on silica gel support at low temperatures and normal pressure.Journal of Catalysis, 88(2), 424-430. doi:10.1016/0021-9517(84)90020-4 White, J. L., & Choi, D. D. (2005). Polyolefins: Processing, Structure Development, and Properties. Zhang, Y., & Yang, W. (1998). Phys.Rev.Lett., 80, 890-890. |
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Academic Press Inc. |
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Facultad de Ciencias Básicas |
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Scopus |
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Universidad de Medellín |
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2017-12-19T19:36:42Z2017-12-19T19:36:42Z2017219517http://hdl.handle.net/11407/425710.1016/j.jcat.2017.08.016reponame:Repositorio Institucional Universidad de Medellíninstname:Universidad de MedellínSilica-supported well-defined Cr(III) sites, which polymerize ethene, are barely reactive towards propene while they copolymerize propene and ethene, a reactivity pattern similar to what is observed for the Phillips catalyst. In contrast to ethene, propene is only polymerized in low amounts and by a small fraction of sites, while during propene/ethene copolymerization small amounts of olefinic oligomers are formed. This difference of reactivity pattern among various olefins is further examined by DFT calculations using periodic amorphous models, focusing on the initiation of polymerization by olefin insertion into the Cr–O bond vs. the heterolytic C–H activation of the alkene. For both mechanisms, we found that the initial activation displays similar energetics for propene and ethene, while the subsequent propene insertion associated with chain growth becomes rather demanding, which rationalizes the observed difference of reactivity between ethene and propene. © 2017 Elsevier Inc.engAcademic Press Inc.Facultad de Ciencias Básicashttps://www.scopus.com/inward/record.uri?eid=2-s2.0-85029025032&doi=10.1016%2fj.jcat.2017.08.016&partnerID=40&md5=2f7fe65684e78b4b350d61d8c50ed0ebJournal of CatalysisJournal of Catalysis Volume 354, 2017, Pages 223-230Ajjou, J. A. N., Scott, S. L., & Paquet, V. (1998). Synthesis and characterization of silica-stabilized chromium(IV) alkylidene complexes. Journal of the American Chemical Society, 120(2), 415-416. doi:10.1021/ja973177aAmor Nait Ajjou, J., & Scott, S. L. (1997). Reactions of tetraalkylchromium(IV) with silica: Mechanism of grafting and characterization of surface organometallic complexes. Organometallics, 16(1), 86-92. doi:10.1021/om960612lArlman, E. J. (1964). Ziegler-natta catalysis II. surface structure of layer-lattice transition metal chlorides. Journal of Catalysis, 3(1), 89-98.Arlman, E. J., & Cossee, P. (1964). Ziegler-natta catalysis III. stereospecific polymerization of propene with the catalyst system TiCl3AlEt3. Journal of Catalysis, 3(1), 99-104.Beck, D. D., & Lunsford, J. H. (1981). The active site for ethylene polymerization over chromium supported on silica. Journal of Catalysis, 68(1), 121-131. doi:10.1016/0021-9517(81)90045-2Braunschweig, H., & Breitling, F. M. (2006). Constrained geometry complexes-synthesis and applications. Coordination Chemistry Reviews, 250(21-22), 2691-2720. doi:10.1016/j.ccr.2005.10.022Brintzinger, H. H., Fischer, D., Mülhaupt, R., Rieger, B., & Waymouth, R. M. (1995). Stereospecific olefin polymerization with chiral metallocene catalysts. Angewandte Chemie International Edition in English, 34(11), 1143-1170. doi:10.1002/anie.199511431Brown, C., Krzystek, J., Achey, R., Lita, A., Fu, R., Meulenberg, R. W., . . . Scott, S. L. (2015). Mechanism of initiation in the phillips ethylene polymerization catalyst: Redox processes leading to the active site.ACS Catalysis, 5(9), 5574-5583. doi:10.1021/acscatal.5b00927Broyden, C. G. (1970). The convergence of single rank quasi newton methods. Mathematics of Computation, 24(110), 365-382. doi:10.1090/S0025-5718-1970-0279993-0Chakrabarti, A., Gierada, M., Handzlik, J., & Wachs, I. E. (2016). Operando molecular spectroscopy during ethylene polymerization by supported CrOx/SiO2 catalysts: Active sites, reaction intermediates, and structure-activity relationship. Topics in Catalysis, 59(8-9), 725-739. doi:10.1007/s11244-016-0546-6Chen, E. Y. -., & Marks, T. J. (2000). Cocatalysts for metal-catalyzed olefin polymerization: Activators, activation processes, and structure-activity relationships. Chemical Reviews, 100(4), 1391-1434. doi:10.1021/cr980462jCheng, R., Liu, Z., Zhong, L., He, X., Qiu, P., Terano, M., . . . Liu, B. (2013). Phillips Cr/silica catalyst for ethylene polymerization doi:10.1007/12-2013-222Coates, G. W. (2000). Precise control of polyolefin stereochemistry using single-site metal catalysts. Chemical Reviews, 100(4), 1223-1252. doi:10.1021/cr990286uCoates, G. W., Hustad, P. D., & Reinartz, S. (2002). Catalysts for the living insertion polymerization of alkenes: Access to new polyolefin architectures using ziegler-natta chemistry. Angewandte Chemie - International Edition, 41(13), 2236-2257. doi:10.1002/1521-3773(20020703)41Comas-Vives, A. (2016). Amorphous SiO2 surface models: Energetics of the dehydroxylation process, strain, ab initio atomistic thermodynamics and IR spectroscopic signatures. Physical Chemistry Chemical Physics, 18(10), 7475-7482. doi:10.1039/c6cp00602gConley, M. P., Delley, M. F., Núnez-Zarur, F., Comas-Vives, A., & Copéret, C. (2015). Heterolytic activation of C-H bonds on CrIII-O surface sites is a key step in catalytic polymerization of ethylene and dehydrogenation of propane. Inorganic Chemistry, 54(11), 5065-5078. doi:10.1021/ic502696nConley, M. P., Delley, M. F., Siddiqi, G., Lapadula, G., Norsic, S., Monteil, V., . . . Copéret, C. (2014). Polymerization of ethylene by silica-supported dinuclear CrIII sites through an initiation step involving C=H bond activation. Angewandte Chemie - International Edition, 53(7), 1872-1876. doi:10.1002/anie.201308983Copéret, C., Chabanas, M., Petroff Saint-Arroman, R., & Basset, J. -. (2003). Surface organometallic chemistry: Homogeneous and heterogeneous catalysis: Bridging the gap through surface organometallic chemistry. Angewandte Chemie - International Edition, 42(2), 156-181. doi:10.1002/anie.200390072Copéret, C., Comas-Vives, A., Conley, M. P., Estes, D. P., Fedorov, A., Mougel, V., . . . Zhizhko, P. A. (2016). Surface organometallic and coordination chemistry toward single-site heterogeneous catalysts: Strategies, methods, structures, and activities. Chemical Reviews, 116(2), 323-421. doi:10.1021/acs.chemrev.5b00373Corradini, P., Guerra, G., & Cavallo, L. (2004). Do new century catalysts unravel the mechanism of stereocontrol of old ziegler-natta catalysts? Accounts of Chemical Research, 37(4), 231-241. doi:10.1021/ar030165nCossee, P. (1964). Ziegler-natta catalysis I. mechanism of polymerization of α-olefins with ziegler-natta catalysts. Journal of Catalysis, 3(1), 80-88.Delley, M. F. (2015). A molecular approach to well-defined metal sites supported on oxides with oxidation state and nuclearity control. Chimia, 69(4), 168-171. doi:10.2533/chimia.2015.168Delley, M. F., Lapadula, G., Núñez-Zarur, F., Comas-Vives, A., Kalendra, V., Jeschke, G., . . . Copéret, C. (2017). Local structures and heterogeneity of silica-supported M(III) sites evidenced by EPR, IR, NMR, and luminescence spectroscopies. Journal of the American Chemical Society, 139(26), 8855-8867. doi:10.1021/jacs.7b02179Delley, M. F., Núñez-Zarur, F., Conley, M. P., Comas-Vives, A., Siddiqi, G., Norsic, S., . . . Copéret, C. (2014). Proton transfers are key elementary steps in ethylene polymerization on isolated chromium(III) silicates. Proceedings of the National Academy of Sciences of the United States of America, 111(32), 11624-11629. doi:10.1073/pnas.1405314111Espelid, Ø., & Børve, K. J. (2002). Molecular-level insight into Cr/silica phillips-type catalysts: Polymerization-active dinuclear chromium sites. Journal of Catalysis, 206(2), 331-338. doi:10.1006/jcat.2001.3499Floryan, L., Borosy, A. P., Núñez-Zarur, F., Comas-Vives, A., & Copéret, C. (2017). Strain effect and dual initiation pathway in CrIII/SiO2polymerization catalysts from amorphous periodic models. Journal of Catalysis, 346, 50-56. doi:10.1016/j.jcat.2016.11.037Fong, A., Peters, B., & Scott, S. L. (2016). One-electron-redox activation of the reduced phillips polymerization catalyst, via alkylchromium(IV) homolysis: A computational assessment. ACS Catalysis, 6(9), 6073-6085. doi:10.1021/acscatal.6b01728Fong, A., Yuan, Y., Ivry, S. L., Scott, S. L., & Peters, B. (2015). Computational kinetic discrimination of ethylene polymerization mechanisms for the phillips (Cr/SiO2) catalyst. ACS Catalysis, 5(6), 3360-3374. doi:10.1021/acscatal.5b00016Fujdala, K. L., & Tilley, T. D. (2003). Design and synthesis of heterogeneous catalysts: The thermolytic molecular precursor approach. Journal of Catalysis, 216(1-2), 265-275. doi:10.1016/S0021-9517(02)00106-9Ghiotti, G., Garrone, E., Coluccia, S., Morterra, C., & Zecchina, A. (1979). Evidence for alkylidenic configuration of polymethylene chains on a phillips catalyst. Journal of the Chemical Society, Chemical Communications, (22), 1032-1033. doi:10.1039/C39790001032Ghiotti, G., Garrone, E., & Zecchina, A. (1988). IR investigation of polymerization centres of the phillips catalyst. Journal of Molecular Catalysis, 46(1-3), 61-77. doi:10.1016/0304-5102(88)85083-1Gierada, M., & Handzlik, J. (2017). Active sites formation and their transformations during ethylene polymerization by the phillips CrOx/SiO2 catalyst. Journal of Catalysis, 352, 314-328. doi:10.1016/j.jcat.2017.05.025Goedecker, S., Teter, M., & Hutter, J. (1996). Separable dual-space gaussian pseudopotentials. Physical Review B - Condensed Matter and Materials Physics, 54(3), 1703-1710.Grimme, S., Antony, J., Ehrlich, S., & Krieg, H. (2010). A consistent and accurate ab initio parametrization of density functional dispersion correction (DFT-D) for the 94 elements H-pu. Journal of Chemical Physics, 132(15) doi:10.1063/1.3382344Grimme, S., Ehrlich, S., & Goerigk, L. (2011). Effect of the damping function in dispersion corrected density functional theory. Journal of Computational Chemistry, 32(7), 1456-1465. doi:10.1002/jcc.21759Groppo, E., Estephane, J., Lamberti, C., Spoto, G., & Zecchina, A. (2007). Ethylene, propylene and ethylene oxide in situ polymerization on the cr(II)/SiO2 system: A temperature- and pressure-dependent investigation. Catalysis Today, 126(1-2), 228-234. doi:10.1016/j.cattod.2007.01.052Groppo, E., Lamberti, C., Bordiga, S., Spoto, G., & Zecchina, A. (2006). In situ FTIR spectroscopy of key intermediates in the first stages of ethylene polymerization on the Cr/SiO2 phillips catalyst: Solving the puzzle of the initiation mechanism? Journal of Catalysis, 240(2), 172-181. doi:10.1016/j.jcat.2006.03.006Groppo, E., Lamberti, C., Bordiga, S., Spoto, G., & Zecchina, A. (2005). The structure of active centers and the ethylene polymerization mechanism on the Cr/SiO2 catalyst: A frontier for the characterization methods. Chemical Reviews, 105(1), 115-183. doi:10.1021/cr040083sGrubbs, R. H., & Coates, G. W. (1996). Acc.Chem.Res., 29, 85-93.Hartwigsen, C., Goedecker, S., & Hutter, J. (1998). Relativistic separable dual-space gaussian pseudopotentials from H to rn. Physical Review B - Condensed Matter and Materials Physics, 58(7), 3641-3662.Ikeda, H., Monoi, T., & Sasaki, Y. (2003). Performance of the cr[CH(SiMe3)2]3/SiO2 catalyst for ethylene polymerization compared with the performance of the phillips catalyst. Journal of Polymer Science, Part A: Polymer Chemistry, 41(3), 413-419. doi:10.1002/pola.10590Ittel, S. D., Johnson, L. K., & Brookhart, M. (2000). Late-metal catalysts for ethylene homo- and copolymerization. Chemical Reviews, 100(4), 1169-1203. doi:10.1021/cr9804644Ivin, K. J., Rooney, J. J., Stewart, C. D., Green, M. L. H., & Mahtab, R. (1978). Mechanism for the stereospecific polymerization of olefins by ziegler-natta catalysts. Journal of the Chemical Society, Chemical Communications, (14), 604-606. doi:10.1039/C39780000604Kakugo, M., Naito, Y., Mizunuma, K., & Miyatake, T. (1982). 13C NMR determination of monomer sequence distribution in ethylene-propylene copolymers prepared with δ-TiCl3Al(C2H5)2Cl. Macromolecules, 15(4), 1150-1152. doi:10.1021/ma00232a037Kaminsky, W. (2012). Discovery of methylaluminoxane as cocatalyst for olefin polymerization. Macromolecules, 45(8), 3289-3297. doi:10.1021/ma202453uKaminsky, W. (1998). Highly active metallocene catalysts for olefin polymerization. Journal of the Chemical Society - Dalton Transactions, (9), 1413-1418.Krack, M. (2005). Pseudopotentials for H to kr optimized for gradient-corrected exchange-correlation functionals. Theoretical Chemistry Accounts, 114(1-3), 145-152. doi:10.1007/s00214-005-0655-yKrauss, H. L., & Stach, H. (1969). Über oberflächenverbindungen von übergangsmetallen. IV. polymerisationsreaktionen an Oberflächen‐Chrom(II)‐Verbindungen. ZAAC ‐ Journal of Inorganic and General Chemistry, 366(5-6), 280-290. doi:10.1002/zaac.19693660505Liu, B., Nakatani, H., & Terano, M. (2003). Mechanistic implications of the unprecedented transformations of ethene into propene and butene over phillips CrOx/SiO2 catalyst during induction period. Journal of Molecular Catalysis A: Chemical, 201(1-2), 189-197. doi:10.1016/S1381-1169(03)00151-1Liu, D., & Nocedal, J. (1989). Siam.J.Sci.Stat.Comp., 10, 1-17.Liu, H. -., Cai, I. C., Fedorov, A., Ziegler, M. S., Copéret, C., & Tilley, T. D. (2016). Tricoordinate organochromium(III) complexes supported by a bulky silylamido ligand produce ultra-high-molecular weight polyethylene in the absence of activators. Helvetica Chimica Acta, 99(11), 859-867. doi:10.1002/hlca.201600199Liu, Z., He, X., Cheng, R., Eisen, M. S., Terano, M., Scott, S. L., & Liu, B. (2014). Adv.Chem.Eng., 44, 127-191.MacAdams, L. A., Buffone, G. P., Incarvito, C. D., Rheingold, A. L., & Theopold, K. H. (2005). A chromium catalyst for the polymerization of ethylene as a homogeneous model for the phillips catalyst. Journal of the American Chemical Society, 127(4), 1082-1083. doi:10.1021/ja043877xMasson, P., Llauro-Darricades, M. -., Spitz, R., & Cheng, H. N. (1996). A study of the dispersity of catalytic sites in ethylene/propylene copolymerization through computer-assisted 13C NMR analysis.International Journal of Polymer Analysis and Characterization, 2(4), 379-393.McDaniel, M. P. (1985). Supported chromium catalysts for ethylene polymerization doi:10.1016/S0360-0564(08)60258-8Myers, D. L., & Lunsford, J. H. (1985). Silica-supported chromium catalysts for ethylene polymerization. Journal of Catalysis, 92(2), 260-271. doi:10.1016/0021-9517(85)90260-XNakamura, A., Ito, S., & Nozaki, K. (2009). Coordination-insertion copolymerization of fundamental polar monomers. Chemical Reviews, 109(11), 5215-5244. doi:10.1021/cr900079rNocedal, J. (1980). Updating quasi-newton matrices with limited storage. Math.Comput., 35(151), 773-782.Novokshonova, L. A., & Zakharov, V. A. (2013). Kinetics of olefin polymerization and active sites of heterogeneous ziegler-natta catalysts doi:10.1007/12-2013-227Núñez-Zarur, F., & Comas-Vives, A. (2015). The effect of the electronic nature of spectator ligands in the C-H bond activation of ethylene by cr(III) silicates: An ab initio study. Chimia, 69(4), 225-229. doi:10.2533/chimia.2015.225Pelletier, J. D. A., & Basset, J. -. (2016). Catalysis by design: Well-defined single-site heterogeneous catalysts. Accounts of Chemical Research, 49(4), 664-677. doi:10.1021/acs.accounts.5b00518Perdew, J. P., Burke, K., & Ernzerhof, M. (1996). Generalized gradient approximation made simple. Physical Review Letters, 77(18), 3865-3868. doi:10.1103/PhysRevLett.77.3865Perdew, J. P., Ruzsinszky, A., Csonka, G. I., Vydrov, O. A., Scuseria, G. E., Constantin, L. A., . . . Burke, K. (2008). Restoring the density-gradient expansion for exchange in solids and surfaces. Physical Review Letters, 100(13) doi:10.1103/PhysRevLett.100.136406Przhevalskaya, L. K., Shvets, V. A., & Kazansky, V. B. (1975). The study of active centers of ethylene polymerization over chromium catalysts prepared from tri- and bivalent chromium compounds. Journal of Catalysis, 39(3), 363-368. doi:10.1016/0021-9517(75)90302-4Rappé, A. K., Skiff, W. M., & Casewit, C. J. (2000). Modeling metal-catalyzed olefin polymerization. Chemical Reviews, 100(4), 1435-1456. doi:10.1021/cr9902493Rebenstorf, B. (1988). An IR study of the polymerization mechanism of the phillips catalyst. Journal of Molecular Catalysis, 45(2), 263-274. doi:10.1016/0304-5102(88)80016-6Rebenstorf, B., & Larsson, R. (1981). Why do homogeneous analogs of phillips (CrO3/SiO2) and union carbide (Chromocene/SiO2) polyethylene catalysts fail? some answers from ir investigations. Journal of Molecular Catalysis, 11(2-3), 247-256. doi:10.1016/0304-5102(81)87012-5Shanno, D. F., & Kettler, P. C. (1970). Optimal conditioning of quasi-newton methods. Mathematics of Computation, 24(111), 657-664. doi:10.1090/S0025-5718-1970-0274030-6Stürzel, M., Mihan, S., & Mülhaupt, R. (2016). From multisite polymerization catalysis to sustainable materials and all-polyolefin composites. Chemical Reviews, 116(3), 1398-1433. doi:10.1021/acs.chemrev.5b00310Tada, M., & Iwasawa, Y. (2007). Advanced design of catalytically active reaction space at surfaces for selective catalysis. Coordination Chemistry Reviews, 251(21-24), 2702-2716. doi:10.1016/j.ccr.2007.06.008Theopold, K. H. (1998). Homogeneous chromium catalysts for olefin polymerization. European Journal of Inorganic Chemistry, (1), 15-24. Retrieved from www.scopus.comThomas, B. J., Noh, S. K., Sendlinger, S. C., & Schulte, G. K. (1991). Paramagnetic alkylchromium compounds as homogeneous catalysts for the polymerization of ethylene. Journal of the American Chemical Society, 113(3), 893-902. doi:10.1021/ja00003a024VandeVondele, J., & Hutter, J. (2003). An efficient orbital transformation method for electronic structure calculations. Journal of Chemical Physics, 118(10), 4365-4369. doi:10.1063/1.1543154VandeVondele, J., & Hutter, J. (2007). Gaussian basis sets for accurate calculations on molecular systems in gas and condensed phases. Journal of Chemical Physics, 127(11) doi:10.1063/1.2770708Weckhuysen, B. M., & Schoonheydt, R. A. (1999). Olefin polymerization over supported chromium oxide catalysts. Catalysis Today, 51(2), 215-221.Wegener, S. L., Marks, T. J., & Stair, P. C. (2012). Design strategies for the molecular level synthesis of supported catalysts. Accounts of Chemical Research, 45(2), 206-214. doi:10.1021/ar2001342Weiss, K., & Krauss, H. -. (1984). Surface compounds of transition metals. XXVIII. polymerization of n-1-alkenes with surface chromium(II) on silica gel support at low temperatures and normal pressure.Journal of Catalysis, 88(2), 424-430. doi:10.1016/0021-9517(84)90020-4White, J. L., & Choi, D. D. (2005). Polyolefins: Processing, Structure Development, and Properties.Zhang, Y., & Yang, W. (1998). Phys.Rev.Lett., 80, 890-890.ScopusOlefin polymerization on Cr(III)/SiO2: Mechanistic insights from the differences in reactivity between ethene and propeneArticleinfo:eu-repo/semantics/articlehttp://purl.org/coar/version/c_970fb48d4fbd8a85http://purl.org/coar/resource_type/c_6501http://purl.org/coar/resource_type/c_2df8fbb1Delley, M.F., ETH Zürich, Department of Chemistry and Applied Biosciences, Vladimir-Prelog-Weg 1-5, Zürich, SwitzerlandPraveen, C.S., ETH Zürich, Department of Chemistry and Applied Biosciences, Vladimir-Prelog-Weg 1-5, Zürich, SwitzerlandBorosy, A.P., ETH Zürich, Department of Chemistry and Applied Biosciences, Vladimir-Prelog-Weg 1-5, Zürich, SwitzerlandNúñez-Zarur, F., ETH Zürich, Department of Chemistry and Applied Biosciences, Vladimir-Prelog-Weg 1-5, Zürich, Switzerland, Facultad de Facultad de Ciencias Básicas, Universidad de Medellín, Carrera 87 N° 30-65, Medellín, ColombiaComas-Vives, A., ETH Zürich, Department of Chemistry and Applied Biosciences, Vladimir-Prelog-Weg 1-5, Zürich, SwitzerlandCopéret, C., ETH Zürich, Department of Chemistry and Applied Biosciences, Vladimir-Prelog-Weg 1-5, Zürich, SwitzerlandDelley M.F.Praveen C.S.Borosy A.P.Núñez-Zarur F.Comas-Vives A.Copéret C.ETH Zürich, Department of Chemistry and Applied Biosciences, Vladimir-Prelog-Weg 1-5, Zürich, SwitzerlandFacultad de Facultad de Ciencias Básicas, Universidad de Medellín, Carrera 87 N° 30-65, Medellín, ColombiaAmorphous modelCrIII sitesDFT calculationsEthene polymerizationPropene polymerizationSilicaSilica-supported well-defined Cr(III) sites, which polymerize ethene, are barely reactive towards propene while they copolymerize propene and ethene, a reactivity pattern similar to what is observed for the Phillips catalyst. In contrast to ethene, propene is only polymerized in low amounts and by a small fraction of sites, while during propene/ethene copolymerization small amounts of olefinic oligomers are formed. This difference of reactivity pattern among various olefins is further examined by DFT calculations using periodic amorphous models, focusing on the initiation of polymerization by olefin insertion into the Cr–O bond vs. the heterolytic C–H activation of the alkene. For both mechanisms, we found that the initial activation displays similar energetics for propene and ethene, while the subsequent propene insertion associated with chain growth becomes rather demanding, which rationalizes the observed difference of reactivity between ethene and propene. © 2017 Elsevier Inc.http://purl.org/coar/access_right/c_16ec11407/4257oai:repository.udem.edu.co:11407/42572020-05-27 16:32:48.845Repositorio Institucional Universidad de Medellinrepositorio@udem.edu.co |