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Vanadium(V) Oxo and Imido Calix[8]arene Complexes: Synthesis, Structural Studies, and Ethylene Homo/Copolymerisation Capability
Author(s) -
Redshaw Carl,
Walton Mark J.,
Lee Darren S.,
Jiang Chengying,
Elsegood Mark R. J.,
Michiue Kenji
Publication year - 2015
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201406084
Subject(s) - acetonitrile , chemistry , lithium (medication) , vanadium , medicinal chemistry , alkali metal , ethylene , stereochemistry , crystallization , catalysis , inorganic chemistry , organic chemistry , medicine , endocrinology
Interaction of p ‐ tert ‐butylcalix[8]areneH 8 (L 8 H 8 ) with [NaVO(O t Bu) 4 ] (formed in situ from VOCl 3 ) afforded the complex [Na(NCMe) 5 ][(VO) 2 L 8 H]⋅4 MeCN ( 1 ⋅4 MeCN). Increasing [NaVO(O t Bu) 4 ] to 4 equiv led to [Na(NCMe) 6 ] 2 [(Na(VO) 4 L 8 )(Na(NCMe)) 3 ] 2 ⋅10 MeCN ( 2 ⋅10 MeCN). With adventitious oxygen, reaction of 4 equiv of [VO(O t Bu) 3 ] with L 8 H 8 afforded the alkali‐metal‐free complex [(VO) 4 L 8 (μ 3 ‐O) 2 ] ( 3 ); solvates 3 ⋅3 MeCN and 3 ⋅3 CH 2 Cl 2 were isolated. For the lithium analogue, the order of addition had to be reversed such that lithium tert ‐butoxide was added to L 8 H 8 and then treated with 2 equiv of VOCl 3 ; crystallisation afforded [(VO 2 ) 2 Li 6 [L 8 ](thf) 2 (O t Bu) 2 (Et 2 O) 2 ]⋅Et 2 O ( 4 ⋅Et 2 O). Upon extraction into acetonitrile, [Li(NCMe) 4 ][(VO) 2 L 8 H]⋅8 MeCN ( 5 ⋅8 MeCN) was formed. Use of the imido precursors [V(N t Bu)(O t Bu) 3 ] and [V(N p ‐tolyl)(O t Bu) 3 ] and L 8 H 8 , afforded [ t BuNH 3 ][{V( p ‐tolylN)} 2 L 8 H]⋅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)Cl 2 ]. For copolymerisation, incorporation of propylene was 7.1–10.9 mol % (compare 10 mol % for [VO(OEt)Cl 2 ]), although catalytic activities were lower than [VO(OEt)Cl 2 ].