Issue 15, 2010

Synthesis and ethylene trimerisation capability of new chromium(ii) and chromium(iii) heteroscorpionate complexes

Abstract

Reaction of (Me2pz)2CHSiMe2N(H)R (R = iPr or Ph) or (Me2pz)2CHSiMe2NMe2 with CrCl3(THF)3 or CrCl2(THF)2 gave Cr{(Me2pz)2CHSiMe2NR1R2}Cl3 (R1 = H, R2 = iPr (10) or Ph (11); R1 = R2 = Me (15)) or Cr{(Me2pz)2CHSiMe2NR1R2}Cl2(THF) (R1 = H, R2 = iPr (12) or Ph (13); R1 = R2 = Me (16)), respectively. Compounds 10 and 11 were crystallographically characterized and the magnetic behaviour of all the new compounds was evaluated using SQUID magnetometry. Reaction of CrCl3(THF)3 with Li{C(Me2pz)3}(THF) gave the zwitterionic complex Cr{C(Me2pz)3}Cl2(THF) (17) containing an apical carbanion. Reaction of the analogous phenol-based ligand (Me2pz)2CHArOH (ArO = 2-O-3,5-C6H2tBu2) with CrCl3(THF)3 gave Cr{(Me2pz)2CHArOH}Cl3 (19) whereas the corresponding reaction with CrCl2(THF)2 unexpectedly gave the Cr(III) phenolate derivative Cr{(Me2pz)2CHArO}Cl2(THF) (20) which could also be prepared from CrCl3(THF)3 and the sodiated ligand [Na{(Me2pz)2CHArO}(THF)]2. Reaction of the corresponding ether (Me2pz)2CHArOMe with CrCl3(THF)3 or CrCl2(THF)2 gave Cr{(Me2pz)2CHArOMe}Cl3 (23) and Cr{(Me2pz)2CHArOMe}Cl2(THF) (24), respectively. The catalytic performance in ethylene oligomerisation/polymerisation of all of the new Cr(II) and Cr(III) complexes was evaluated. Most of the complexes showed high activity, but produced a Schultz-Flory distribution of α-olefins. Compound 23 had an exceptionally low α-value of 0.37 and showed a preference for 1-hexene and 1-octene formation. While replacing a secondary amine (10-13) for a tertiary amine (15-16) resulted in loss of catalytic activity, replacing a phenol (19) for an anisole (23) group afforded a more selective and more active catalyst. Changing from MAO to DIBAL-O as cocatalyst induced a switch in selectivity to ethylene polymerisation.

Graphical abstract: Synthesis and ethylene trimerisation capability of new chromium(ii) and chromium(iii) heteroscorpionate complexes

Supplementary files

Article information

Article type
Paper
Submitted
14 Dec 2009
Accepted
09 Feb 2010
First published
05 Mar 2010

Dalton Trans., 2010,39, 3653-3664

Synthesis and ethylene trimerisation capability of new chromium(II) and chromium(III) heteroscorpionate complexes

A. F. R. Kilpatrick, S. V. Kulangara, M. G. Cushion, R. Duchateau and P. Mountford, Dalton Trans., 2010, 39, 3653 DOI: 10.1039/B926333K

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements