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Activation of [CrCl3{PPh2N(iPr)PPh2}] for the selective oligomerisation of ethene: a Cr K-edge XAFS study

Citation

Bartlett, SA and Moulin, J and Tromp, M and Reid, G and Dent, AJJ and Cibin, G and McGuinness, DS and Evans, John, Activation of [CrCl3{PPh2N(iPr)PPh2}] for the selective oligomerisation of ethene: a Cr K-edge XAFS study, Catalysis Science & Technology, 6, (16) pp. 6237-6246. ISSN 2044-4753 (2016) [Refereed Article]

Copyright Statement

Copyright 2016 The Royal Society of Chemistry

DOI: doi:10.1039/c6cy00902f

Abstract

The activation of the ethene tetramerisation catalyst system based upon [CrCl3(THF)3] and N(iPr)(PPh2)2 has been investigated in situ via the reaction of [CrCl3{PPh2N(R)PPh2}(THF)] 1a (R = iPr) with excess AlMe3 in toluene. The Cr K-edge XAFS spectrum of the solution freeze quenched after 1 min reaction time indicated monomethylation of the metal with the resultant product being [CrClMe(ClAlCl3){PPh2N(R)PPh2}(THF)] 4a (R = iPr). After 5 minutes reaction time the XAFS spectra indicate that ∼50% of 4a had been converted to a Cr(II) species, with the central core being high spin [CrCl2{PPh2N(R)PPh2}] 7a (R = iPr); a similar species, [CrClMe{PPh2N(R)PPh2}] 9a (R = iPr) was observed as its adduct with AlMe3 (10a) (R = iPr) when spectra were recorded on samples maintained at room temperature. Detailed analysis (EXAFS and XANES) indicated that 7a and 9a are stabilised by adduct formation of a CrCl bond to the Lewis acids B(C6F5)3 and AlMe3, respectively. Modelling with DFT methods indicated that five-coordination was achieved, respectively by CrF (11a) and CrC (10a) interactions. In the presence of [Ph3C][Al{OC(tBuF)3}4], the Cr XAFS of the room temperature solution was inconsistent with the maintenance of a phosphine complex, but could be modelled with a site like [Cr2Me8]4− {CrCr 2.01(2), CrC 2.14(4)}, thus demonstrating considerable variation in the effects of differing Lewis acids.

Item Details

Item Type:Refereed Article
Research Division:Chemical Sciences
Research Group:Other Chemical Sciences
Research Field:Organometallic Chemistry
Objective Division:Manufacturing
Objective Group:Industrial Chemicals and Related Products
Objective Field:Organic Industrial Chemicals (excl. Resins, Rubber and Plastics)
Author:McGuinness, DS (Dr David McGuinness)
ID Code:113505
Year Published:2016
Web of Science® Times Cited:1
Deposited By:Chemistry
Deposited On:2017-01-05
Last Modified:2017-03-27
Downloads:0

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