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Sc(iii) complexes with neutral N3- and SNS-donor ligands – a spectroscopic study of the activation of ethene polymerisation catalysts

DOI: 10.1039/c2dt31804k DOI Help

Authors: Stuart Bartlett (University of Southampton) , Giannantonio Cibin (Diamond Light Source) , Andrew Dent (Diamond Light Source Ltd) , John Evans (University of Southampton) , Martin J. Hanton (Sasol Technology UK) , Gillian Reid (University of Southampton) , Robert P. Tooze (Sasol Technology UK) , Moniek Tromp (Southampton University)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Dalton Transactions , VOL 42 (6)

State: Published (Approved)
Published: October 2012
Diamond Proposal Number(s): 7232

Abstract: Scandium trichloride complexes with tridentate N3- and S2N-donor ligands (L3) have been synthesised and characterised by IR, 1H, 13C{1H} and 45Sc NMR spectroscopy, microanalysis, and solid state and solution XAFS spectroscopy. Catalytic testing of a subset of these complexes with ethene has been undertaken in chlorobenzene with MMAO-3A and PMAO-IP at 60 °C and 40 bar ethene, giving low activity ethene polymerisation. The reactions of these complexes with MeLi and AlMe3 were studied by 1H, 13C{1H}, 27Al and 45Sc NMR spectroscopy and in situ via Sc K-edge XAFS spectroscopy. Three or four mol. equivalents of MeLi react with [ScCl3(Me3-tacn)] in THF solution to form [ScMe3(Me3-tacn)] cleanly, while complexes of type [ScCl3(R-SNS)] {R-SNS = HN(CH2CH2SC10H21)2} form two different species proposed to be [ScMe3(R-SN(Li)S)] and [ScMe2(R-SN?S)]. In contrast, in situ45Sc NMR and Sc K-edge XAFS spectroscopic studies of the reaction of [ScCl3(Me3-tacn)] with 10 mol. equivalents of AlMe3 strongly suggest that alkylation at the Sc(III) centre does not occur, instead retaining the Cl3N3 coordination environment and most likely forming Sc?Cl?AlMe3 bridging interactions. Similar studies on [ScCl3(decyl-SNS)] with 10 mol. equivalents of AlMe3 are also consistent with this, indicating that alkylation at the Sc centre does not occur except in the presence of co-catalyst [Ph3C][Al{OC(CF3)3}4] and the ?-alkene, hex-1-ene.

Subject Areas: Chemistry

Instruments: B18-Core EXAFS