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Chiral or not chiral? A case study of the hexanuclear metalloprisms [Cp<sup>*</sup><sub>6</sub>M<sub>6</sub> (µ<sub>3</sub>-tpt-κN)<sub>2</sub>(µ-C<sub>2</sub>O<sub>4</sub>-κO)<sub>3</sub>]<sup>6+</sup> (M = Rh, Ir, tpt = 2,4,6-tri(pyridin-4-yl)-1,3,5-triazine)
Auteur(s)
Govindaswamy, Padavattan
Linder, David
Lacour, Jerôme
Date Issued
2007
Journal
Dalton Transactions, Royal Society of Chemistry (RSC), 2007///4457-4463
Abstract
Cationic hexarhodium and hexairidium complexes with a trigonal prismatic architecture have been synthesised in good yield by self-assembly of the dinuclear oxalato-bridged complexes [Cp*<sub>2</sub>M<sub>2</sub> (µ-C<sub>2</sub>O<sub>4</sub>-κ<i>O</i>)Cl<sub>2</sub>] (M = Rh; <b>1</b>: Ir; <b>2</b>) with 2,4,6-tri(pyridine-4-yl)-1,3,5-triazine (tpt) in the presence of AgO<sub>3</sub>SCF<sub>3</sub>. The trigonal prismatic cations [Cp*<sub>6</sub>Rh<sub>6</sub> (µ<sub>3</sub>-tpt-κ<i>N</i>)2(µ-C<sub>2</sub>O<sub>4</sub>-κ<i>O</i>)<sub>3</sub>]<sup>6+</sup> (<b>3</b>) and [Cp*<sub>6</sub>Ir<sub>6</sub> (µ<sub>3</sub>-tpt-κ<i>N</i>)<sub>2</sub> (µ-C<sub>2</sub>O<sub>4</sub>-κ<i>O</i>)<sub>3</sub>]<sup>6+</sup> (<b>4</b>) have been isolated as their triflate salts. The single-crystal X-ray structure analysis of [<b>3</b>][O<sub>3</sub>SCF<sub>3</sub>]<sub>6</sub> shows two enantiomers in the racemic crystal (space group <i>C</i>2/<i>c</i>), the chirality being due to a twist of the two tpt units. By contrast, the single-crystal X-ray structure analysis of [<b>4</b>][O3SCF3]6 shows a perfectly eclipsed conformation of the tpt units, so that <b>4</b> is not chiral in the crystal state (space group <i>Fd</i>¯3<i>c</i>). However, in solution, enantiodifferentiation in the presence of the chiral anion Δ-BINPHAT is observed by <sup>1</sup>H NMR spectrometry not only in the case of <b>3</b>, but also in the case of <b>4</b>. This suggests that the iridium derivative <b>4</b>, which is not chiral in the solid state, adopts chiral conformations in solution.
Publication type
journal article
