Vanadyl calix[6]arene complexes: synthesis, structural studies and ethylene homo-(co-)polymerization capabilityElectronic supplementary information (ESI) available: X-ray crystallographic files CIF format for the structure determinations of compound 1-5. CCDC 895364 and 950038-950039. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c5dt00376h

• Main Authors: Redshaw, Carl, Walton, Mark, Michiue, Kenji, Chao, Yimin, Walton, Alex, Elo, Pertti, Sumerin, Victor, Jiang, Chengying, Elsegood, Mark R. J
• Format: Journal Article
• Language: English
• Published: 02.07.2015
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/c5dt00376h

Treatment of p-tert -butylcalix[6]areneH 6 (L 6 H 6 ) with in situ [LiVO(O t -Bu) 4 ] afforded, after work-up, the dark green complex [Li(MeCN) 4 ][V 2 (O) 2 Li(MeCN)(L 6 H 2 ) 2 ]·8MeCN ( 1 ·8MeCN). On one occasion, the reaction led to the formation of a mixture of products, the bulk of which differing from 1 only in the amount of solvate, viz. 2 ·9.67MeCN. The second minor, yellow product has the formula {[(VO 2 ) 2 (L 6 H 2 )(Li(MeCN) 2 ) 2 ]·2MeCN} n ( 3 ·2MeCN), and comprises a 1D polymeric structure with links through the L 6 H 2 ligand and Li 2 O 2 units. When the reverse order of addition was employed such that lithium tert -butoxide (7.5 equivalents) was added to L 6 H 6 , and subsequently treated with VOCl 3 (2 equiv.), the complex {[VO(THF)][VO(μ-O)] 2 Li(THF)(Et 2 O)][L 6 ]}·2Et 2 O·0.5THF ( 4 ·2Et 2 O·0.5THF), which contains a trinuclear motif possessing a central, octahedral vanadyl centre linked via oxo bridges to two tetrahedral ( C 3v ) vanadyl centres, was isolated. The calix[6]arene in 4 is severely twisted and adopts a 'down, down, down, down, out, out' conformation. Use of excess lithium tert -butoxide led to a complex very similar to 4 , differing only in the solvent of crystallization, namely 5 ·Et 2 O·2THF. The ability of 1 and 5 to act as pre-catalysts for ethylene polymerization in the presence of a variety of co-catalysts and under various conditions has been investigated. Co-polymerization of ethylene with propylene and with 1-hexene have also been conducted; results are compared versus VO(OEt)Cl 2 . Use of various combinations of [VOCl 3 ], LiO t -Bu and p-tert -butylcalix[6]areneH 6 affords vanadyl complexes capable of ethylene homo-(co-)polymerization.