Synthesis, characterisation and structures of thio-, seleno- and telluro-ether complexes of indium(III) halides

Abstract

The indium(III) halo-bridged octahedral dimers [InX₂(L–L)(μ-X)₂InX₂(L–L)] (X = Cl: L–L = MeS(CH₂)₂SMe, MeSe(CH₂)₂SeMe, ⁿBuSe(CH₂)₂SeⁿBu), the ionic trans-[InX₂(L–L)₂][InX₄] (X = Cl: L–L = ⁱPrS(CH₂)₂SⁱPr; X = Br: L–L = MeS(CH₂)₂SMe, ⁱPrS(CH₂)₂SⁱPr, MeSe(CH₂)₂SeMe), cis-[InCl₂(thiamacrocycle)][InCl₄] (thiamacrocycle = [12]aneS₄ or [14]aneS₄) and the neutral, octahedral [InCl₃([9]aneS₃)] and [InCl₃{MeC(CH₂SMe)₃}] were obtained in good yield by the reaction of 1:1 molar ratios of InX₃ with the ligand in anhydrous CH₂Cl₂ solution. The distorted tetrahedral [InX₃(Me₂Se)] (X = Cl, Br or I) and [InX₃(Me₂Te)] (X = Br or I) were obtained from 1:3 and 1:2 molar ratios respectively of InX₃ and Me₂E (E = Se or Te) also in CH₂Cl₂. The ligand-bridged, distorted tetrahedral dimers [(InCl₃)₂{μ₂-o-C₆H₄(CH₂SMe)₂}] and [(InCl₃)₂{μ₂-MeTe(CH₂)₃TeMe}] are formed even from a 1:1 In:ligand ratio. Key structure types were confirmed from crystal structures of [InCl₂{RSe(CH₂)₂SeR}(μ-Cl)₂InCl₂{RSe(CH₂)₂SeR₂}] (R = Me or ⁿBu), trans-[InX₂{ⁱPrS(CH₂)₂SⁱPr}₂][InX₄] (X = Cl or Br), trans-[InBr₂{MeSe(CH₂)₂SeMe}₂][InBr₄], cis-[InCl₂([14]aneS₄)][InCl₄] and [InBr₃(Me₂Se)]. The bulk complexes have been characterised by IR and Raman spectroscopy and microanalyses, while ¹H, ⁷⁷Se{¹H} and ¹²⁵Te{¹H} NMR spectroscopy show that the compounds are extremely labile in solution and undergo rapid dynamic exchange equilibria. Comparisons are drawn between these structurally rather diverse In(III) chalcogenoether complexes and the corresponding Ga(III) species (all of which are neutral and involve distorted tetrahedral coordination). The reaction of TlCl₃ with Me₂E (E = Se or Te) shows that chlorination of Me₂E rather than adduct formation occurs, while no reaction occurred between TlCl₃ and Me₂S, consistent with Tl(III) being a very poor Lewis acid.