Issue 38, 2009

Calixarene-monophosphines as supramolecular chelators

Abstract

The calix[4]arenes 5-diphenylphosphino-17-R1-11,23-diR2-25,26,27,28-tetrapropoxycalix[4]arene (1, R1 = R2 = Br; 2, R1 = Br, R2 = H; 3, R1 = R2 = p-tolyl; 4, R1 = p-tolyl, R2 = H; 5, R1 = R2 = H; 20, R1 = p-tolyl, R2 = H), all bearing a diphenylphosphino group attached to the calixarene upper rim, have been synthesised starting from 5,11,17,23-tetrabromo-25,26,27,28-tetrapropoxycalix[4]arene. Reaction of 1–5 with [RuCl2(p-cymene)]2 leads quantitatively to monophosphine complexes, [RuCl2(p-cymene)L], in which the endo-oriented ruthenium atom unit sits inside the cone delineated by the four phenoxy rings. The particular orientation of the P–Ru vector appears to result from π–π interactions between the p-cymene ligand and two aromatic cavity walls. Overall, in each case the calixarene end of the ligand behaves as a supramolecular receptor towards the Ru(p-cymene) fragment. Formation of complexes with exo-oriented P–M bonds were observed in the complexes cis-[PtCl2·12] and in [RuCl2(p-cymene)·20]. As shown by a variable temperature study carried out on [RuCl2(p-cymene)·3], in which the ruthenium is embedded in an expanded cone, the p-cymene ring undergoes a fast oscillation about the Ru-arene bond which can be frozen out at low temperatures. Reaction of [RuCl2(p-cymene)·3] with AgBF4 in CH3CN results in an intra-cavity reaction, with one chloride ligand being replaced by acetonitrile.

Graphical abstract: Calixarene-monophosphines as supramolecular chelators

Supplementary files

Article information

Article type
Paper
Submitted
07 Apr 2009
Accepted
07 Jul 2009
First published
05 Aug 2009

Dalton Trans., 2009, 7912-7923

Calixarene-monophosphines as supramolecular chelators

S. Sameni, M. Lejeune, C. Jeunesse, D. Matt and R. Welter, Dalton Trans., 2009, 7912 DOI: 10.1039/B907100H

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