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Ethylene trimerization with mixed-donor ligand (N,P,S) chromium complexes: Effect of ligand structure on activity and selectivity

journal contribution
posted on 2023-05-16, 19:50 authored by McGuinness, DS, Wasserscheid, P, Morgan, DH, Dixon, JT
Methylaluminoxane (MAO)-activated chromium(III) complexes of tridentate PNP and SNS ligands of the form (R2PCH2CH2) 2NR′ (R = alkyl, aryl; R′ = H, Me, benzyl) and (RSCH 2-CH2)2NH (R = alkyl) have been prepared and tested for the trimerization of ethylene to 1-hexene. The effect of P or S donor substitution, nitrogen substitution, and chelate ring size has been examined. Sterically compact and basic P or S groups lead to the highest activities and selectivities, while a secondary amine central donor is crucial for high activity, raising the possibility that deprotonation of this group occurs during catalyst formation. Expanding the chelate ring size by introduction of a propyl spacer on one side of the SNS ligand gives EtSC3H 6N(H)C2H4SEt, which leads to a trimerization catalyst with lower activity. The scope of S-donor-based ligands for ethylene trimerization was further studied by preparing and testing PSP and SPS tridentates of CrIII. These complexes give rise to active oligomerization systems that give product distributions characteristic of both linear chain growth and selective trimerization.

History

Publication title

Organometallics

Volume

24

Issue

4

Pagination

552-556

ISSN

0276-7333

Department/School

School of Natural Sciences

Publisher

American Chemical Society

Place of publication

Washington

Repository Status

  • Restricted

Socio-economic Objectives

Organic industrial chemicals (excl. resins, rubber and plastics)

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