Chiral or not chiral? A case study of the hexanuclear metalloprisms [Cp^*₆M₆ (µ₃-tpt-κN)₂(µ-C₂O₄-κO)₃]⁶⁺ (M = Rh, Ir, tpt = 2,4,6-tri(pyridin-4-yl)-1,3,5-triazine)

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*₂M₂ (µ-C₂O₄-κ<i>O</i>)Cl₂] (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 AgO₃SCF₃. The trigonal prismatic cations [Cp*₆Rh₆ (µ₃-tpt-κ<i>N</i>)2(µ-C₂O₄-κ<i>O</i>)₃]⁶⁺ (<b>3</b>) and [Cp*₆Ir₆ (µ₃-tpt-κ<i>N</i>)₂ (µ-C₂O₄-κ<i>O</i>)₃]⁶⁺ (<b>4</b>) have been isolated as their triflate salts. The single-crystal X-ray structure analysis of [<b>3</b>][O₃SCF₃]₆ 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 ¹H 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.