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Title: Vanadium(V) oxo and Imido calix[8]arene complexes: synthesis, structural studies, and ethylene homo/copolymerisation capability
Authors: Redshaw, Carl
Walton, Mark J.
Lee, Darren S.
Jiang, Chengying
Elsegood, Mark R.J.
Michiue, Kenji
Keywords: Calix[8]arene
Copolymerisation
Ethylene polymerisation
Vanadium
X-ray diffraction
Issue Date: 2015
Publisher: © Wiley-VCH Verlag GmbH & Co.
Citation: REDSHAW, C. et al., 2015. Vanadium(V) oxo and imido calix[8]arene complexes: synthesis, structural studies, and ethylene homo/copolymerisation capability. Chemistry - A European Journal, 21 (13), pp.5199-5210
Abstract: Interaction of p-tert-butylcalix[8]areneH8 (L8H8) with [NaVO(OtBu)4] (formed in situ from VOCl3) afforded the complex [Na(NCMe)5][(VO)2L8H]·4 MeCN (1·4 MeCN). Increasing [NaVO(OtBu)4] to 4 equiv led to [Na(NCMe)6]2[(Na(VO)4L8)(Na(NCMe))3]2·10 MeCN (2·10 MeCN). With adventitious oxygen, reaction of 4 equiv of [VO(OtBu)3] with L8H8 afforded the alkali-metal-free complex [(VO)4L8(μ3-O)2] (3); solvates 3×3 MeCN and 3×3 CH2Cl2 were isolated. For the lithium analogue, the order of addition had to be reversed such that lithium tert-butoxide was added to L8H8 and then treated with 2 equiv of VOCl3; crystallisation afforded [(VO2)2Li6[L8](thf)2(OtBu)2(Et2O)2]·Et2O (4·Et2O). Upon extraction into acetonitrile, [Li(NCMe)4][(VO)2L8H]·8 MeCN (5·8 MeCN) was formed. Use of the imido precursors [V(NtBu)(OtBu)3] and [V(Np-tolyl)(OtBu)3] and L8H8, afforded [tBuNH3][{V(p-tolylN)}2L8H]·3 1/2 MeCN (6·3 1/2 MeCN). The molecular structures of 1 to 6 are reported. Complexes 1, 3, and 4 were screened as precatalysts for the polymerisation of ethylene in the presence of cocatalysts at various temperatures and for the copolymerisation of ethylene with propylene. Activities as high as 136 000 g (mmol(V) h)-1 were sometimes achieved; higher molecular weight polymers could be obtained versus the benchmark [VO(OEt)Cl2]. For copolymerisation, incorporation of propylene was 7.1-10.9 mol% (compare 10 mol% for [VO(OEt)Cl2]), although catalytic activities were lower than [VO(OEt)Cl2].
Description: This is the peer reviewed version of the article which has been published in final form at http://dx.doi.org/10.1002/chem.201406084 This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.
Sponsor: The EPSRC and STFC are thanked for financial support (including an Overseas Travel grant to C.R.).
Version: Accepted for publication
DOI: 10.1002/chem.201406084
URI: https://dspace.lboro.ac.uk/2134/18062
Publisher Link: http://dx.doi.org/10.1002/chem.201406084
ISSN: 0947-6539
Appears in Collections:Published Articles (Chemistry)

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