Role of the ligand and activator in selective Cr–PNP ethene tri- and tetramerization catalysts – a spectroscopic study

DOI: 10.1039/D0CY01168A

Authors: Bas Venderbosch (University of Amsterdam) , Lukas A. Wolzak (University of Amsterdam) , Jean-pierre H. Oudsen (University of Amsterdam) , Bas De Bruin (University of Amsterdam) , Ties J. Korstanje (University of Amsterdam) , Moniek Tromp (University of Groningen)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Catalysis Science & Technology , VOL 91

State: Published (Approved)
Published: August 2020
Diamond Proposal Number(s): 22331

Abstract: The reaction of the ethene tetramerization catalyst, ((C6H5)2P)2NiPrCrCl3(THF) (complex 1), and ethene trimerization catalyst, ((o-C6H4OMe)2P)2NMeCrCl3 (complex 2), with alkylaluminum reagents (AlMe3 and MMAO) was investigated using spectroscopic techniques (Cr K-edge XAS, X-band EPR and UV-vis) and catalytic studies. In all cases the majority of chromium was reduced to the divalent oxidation state and only a minor fraction of chromium was reduced further to the monovalent oxidation state. It is demonstrated that MMAO and the ligand (through a pendant ether donor) can facilitate ion pair formation for these divalent Cr complexes, providing insights into the role of the ligand and activator in the activation process. Via the use of dienes, we succeeded in characterizing a monocationic CrII alkene complex, providing evidence that catalysis could proceed via cationic CrII/CrIV intermediates. This is supported by DFT calculations, where it is shown that a mechanism proceeding via dicationic CrII/CrIV intermediates explains the observed product selectivity.

Subject Areas: Chemistry


Instruments: B18-Core EXAFS

Other Facilities: SuperXAS at Swiss Light Source

Documents:
d0cy01168a.pdf

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