Issue 7, 2009

New structural motifs in chromium(iii) calix[4 and 6]arene chemistry

Abstract

The reactions of either p-tert-butylcalix[4]areneH4 [Cax(OH)4], 1,3-dimethoxy-p-tert-butylcalix[4]areneH2 [Cax(OH)2(OMe)2] or p-tert-butylcalix[6]areneH6 [Cax[6](OH)6] with alkali metal cations and the chromium complexes [CrCl3(THF)3] or [CrCl2(THF)] (THF = tetrahydrofuran) are described. In particular, the treatment of [Cax(OH)4] with in situ generated M[Cr(Ot-Bu)4] (M = Li or K) affords, after work-up, the complex {[CrCax(O)4(NCMe)]2[Li(THF)]2[Li(NCMe)]2Cl24-O)}·2.25(MeCN) (1) and two forms of {K(MeCN)x[CrCax(O)4(NCMe)][CrCax(OH)(O)3(NCMe)]}·MeCN (x = 3 or 4) (2), respectively. The potassium salt of [Cax(OH)4] reacts with [CrCl2(THF)] to afford a highly sensitive complex, which on exposure to air gives rise to the compound {[CrCax(O)4K(THF)2]2H(μ-O)(H2O)K(THF)(H2O)(μ-THF)}2·6THF (3), that possesses four chromium calixarene units, two sets of K+ ions that are coordinated in two very different environments together with terminal and bridging THF ligands. The reaction of n-BuLi with [Cax(OH)4], followed by the addition of [CrCl3(THF)3] affords, after work-up, the complex {Cr[μ-Cax(OH)(O)3](NCMe)}2·4Me2C[double bond, length as m-dash]O·0.5H2O (4). Complex 4 is also available via the hydrolysis of complex 1. Interaction of [Cax(OH)2(OMe)2] with NaH or n-BuLi in THF affords, following the addition of [CrCl3(THF)3], the demethylated dimer {Cr[μ-Cax(OH)(O)3](NCMe)}2·4MeCN (5), which is a different solvate of 4, or the monomeric salt {Cax(O)2(OMe)2CrCl2[Li(NCMe)2]}·2MeCN (6), respectively. The reaction of 1,3-dipropoxy-p-tert-butylcalix[4]areneH2, [Cax(OH)2(On-Pr)2], with n-BuLi followed by [CrCl3(THF)3] affords the monomeric complex [CrCl2Cax(O)2(On-Pr)2Li(NCMe)2]·3MeCN (7). Interaction of the mono-methoxy ligand [Cax(OH)3(OMe)] with n-BuLi in diethyl ether followed by addition of [CrCl3(THF)3] in THF affords, upon work-up, the complex [CrCax(OMe)(O)3(NCMe)]2·MeCN (8). Interaction of p-tert-butylcalix[6]areneH6 [Cax[6](OH)6] with Na[Cr(Ot-Bu)4] (formed in situ from [CrCl3(THF)3] and excess NaOt-Bu) affords the complex {CrCax[6](O)3(OH)3Na(NCMe)2(μ-OH)}2·4MeCN (9). Complexes 19 have been structurally characterised; for 3 and 8, it was necessary to use synchrotron radiation. Screening of 19 for ethylene polymerisation using either methylaluminoxane (MAO) or dimethylaluminium chloride (DMAC) as co-catalyst afforded only very poor catalytic activities (≤ 1 g mmol−1 hr−1bar−1).

Graphical abstract: New structural motifs in chromium(iii) calix[4 and 6]arene chemistry

Supplementary files

Article information

Article type
Paper
Submitted
01 Aug 2008
Accepted
31 Oct 2008
First published
16 Dec 2008

Dalton Trans., 2009, 1231-1242

New structural motifs in chromium(III) calix[4 and 6]arene chemistry

C. Redshaw, D. Homden, D. L. Hughes, J. A. Wright and M. R. J. Elsegood, Dalton Trans., 2009, 1231 DOI: 10.1039/B813313A

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements