Issue 8, 2002

Positioning of transition metal centres at the upper rim of cone-shaped calix[4]arenes. Filling the basket with an organometallic ruthenium unit

Abstract

A series of calix[4]arenes bearing diphenylphosphino groups tethered at the upper rim have been prepared by treatment of 5,11,17,23-tetrabromo-25,26,27,28-tetrapropoxycalix[4]arene with ButLi (or BunLi) followed by reaction with PPh2Cl. The tetraphosphinated derivative 3 was found suitable for the formation of tetranuclear species, notably [3·(AuCl)4], [3·{RuCl2(p-cymene)}4], and [3·{PdCl(o-C6H4CH2NMe2)}4], all possessing an apparent C4v-symmetry in solution. Reaction of [RuCl2(p-cymene)]2 with the diphosphines 5,17-di-X-11,23-bis(diphenylphosphino)-25,26,27,28-tetrapropoxycalix[4]arene (X = H, 1; X = Br, 4) afforded the C2v-symmetrical dinuclear complexes [1·{RuCl2(p-cymene)}2] and [4·{RuCl2(p-cymene)}2], respectively. Reaction of the non-brominated diphosphine 1 with [PdCl(o-C6H4CH2NMe2)]2 gave the complex [1·{PdCl(o-C6H4CH2NMe2)}2]. Reaction at high dilution of [PtCl2(1,5-cyclooctadiene)] with 4 or 1 resulted in quantitative formation of the corresponding cis-chelate complexes [4·PtCl2] (12) and [1·PtCl2] (13), respectively. The trans version of 13 could also be obtained, provided that [PtCl2(PhCN)2] was used as starting complex. In the solid state, the PtCl2 unit of 12 is directed towards one bromine atom, resulting in a highly unsymmetrical calixarene structure where the metal plane is nearly parallel to the calix reference plane. The NMR spectra of 12 and 13 show an apparent C2v-symmetrical structure, suggesting a fast fan-like motion in solution of the metal plane about the P⋯P axis. Similar dynamics are likely to occur in the related cationic complexes [1·Rh(norbornadiene)]BF4 (15) and [1·Pd(Me-allyl)]BF4 (16). As shown by variable temperature studies carried out on 12 and 16, these dynamics couple with a concomitant, restricted rotation of the two PPh2 units about their coordination axis. The latter motion is probably a result of steric interactions within the phosphorus environment, two PPh rings being in competition for occupation of the cavity entrance. Reaction of the expanded cavity 5,11,17-tribromo-23-diphenylphosphino-25,26,27,28-tetrapropoxycalix[4]arene 5 with [RuCl2(p-cymene)]2 afforded the monophosphine complex [5·RuCl2(p-cymene)]. In solution as well in the solid state, the p-cymene ligand fills the calixarene basket.

Graphical abstract: Positioning of transition metal centres at the upper rim of cone-shaped calix[4]arenes. Filling the basket with an organometallic ruthenium unit

Supplementary files

Article information

Article type
Paper
Submitted
27 Nov 2001
Accepted
26 Feb 2002
First published
25 Mar 2002

J. Chem. Soc., Dalton Trans., 2002, 1642-1650

Positioning of transition metal centres at the upper rim of cone-shaped calix[4]arenes. Filling the basket with an organometallic ruthenium unit

M. Lejeune, C. Jeunesse, D. Matt, N. Kyritsakas, R. Welter and J. Kintzinger, J. Chem. Soc., Dalton Trans., 2002, 1642 DOI: 10.1039/B110884K

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