Crowded diphosphinomethane ligands in catalysis

• Verfasst von: Schultz, Madeleine [VerfasserIn]
• Verfasst von: Eisenträger, Frank [VerfasserIn]
• Verfasst von: Regius, Christian Thomas [VerfasserIn]
• Verfasst von: Rominger, Frank [VerfasserIn]
• Verfasst von: Hanno-Igels, Patrick [VerfasserIn]
• Verfasst von: Jakob, Paul [VerfasserIn]
• Verfasst von: Pundt-Gruber, Irene [VerfasserIn]
• Verfasst von: Hofmann, Peter [VerfasserIn]
• Titel: Crowded diphosphinomethane ligands in catalysis
• Titelzusatz: ((R2PCH2PR′2-κ2P)NiR″)+ cations for ethylene polymerization without activators
• Verf.angabe: Madeleine Schultz, Frank Eisenträger, Christian Regius, Frank Rominger, Patrick Hanno-Igels, Paul Jakob, Irene Gruber, and Peter Hofmann
• Jahr: 2012
• Umfang: 18 S.
• Teil: volume:31
• Teil: year:2012
• Teil: number:1
• Teil: pages:207-224
• Teil: extent:18
• Fussnoten: Published online: December 27, 2011 ; Gesehen am 30.04.2018
• Titel Quelle: Enthalten in: Organometallics
• Ort Quelle: Washington, DC : ACS Publ., 1982
• Jahr Quelle: 2012
• Band/Heft Quelle: 31(2012), 1, Seite 207-224
• ISSN Quelle: 1520-6041
• DOI: doi:10.1021/om200715w
• Datenträger: Online-Ressource
• Sprache: eng
• K10plus-PPN: 1572486759

Abstract

The preparation of a series of nickel dichloride complexes with bulky diphosphinomethane chelate ligands R2PCH2PR′2 is reported. Reaction with the appropriate Grignardreagent leads to the corresponding dimethyl and dibenzyl complexes. Cationic monomethyl and mono-η3-benzyl complexes are generated from these dialkyl complexes by protonation with [H(OEt2)2]+[B(3,5-(CF3)2C6H3)4]−, while the complex [(dtbpm-κ2P)Ni(η3-CH(CH2Ph)Ph]+[B(3,5-(CF3)2C6H3)4]− is obtained from protonation of the Ni(0) olefin complex (dtbpm-κ2P)Ni(η2-trans-stilbene). Crystal structures of examples of dichlorides, dimethyl, dibenzyl, cationic methyl, and cationic η3-benzyl complexes are reported. Solutions of the cations polymerize ethylene under mild conditions and without the necessity of an activating agent, to form polyethylene having high molecular weights and low degrees of chain branching. In comparison to the Ni methyl cations, the η3-benzyl cation complexes are more stable and somewhat less active but still very efficient in C2H4 polymerization. The effect on the resulting polyethylene of varying the substituents R, R′ on the phosphine ligand has been examined, and a clear trend for longer chain PE with less branching in the presence of more bulky substituents on the diphosphine has been found. Density functional calculations have been used to examine the rapid suprafacial η3 to η3 haptotropic shift processes of the [(R2PCH2PR′2)Ni] fragment and the η3-η1 change of the coordination mode of the benzyl group required for polymerization in those cations.