Synthesis, characterisation and coordinating properties of the small ring S2Te-donor macrocycles [9]aneS2Te, [11]aneS2Te and [12]aneS2Te

Abstract

The reaction of Na₂Te with various α,ω-dichlorodithioether reagents in thf–NH₃(l) at ca. −78 °C produces moderate yields of the [1+1] cyclisation products, [9]aneS₂Te (1,4-dithia-7-telluracyclononane), [11]aneS₂Te (1,4-dithia-8-telluracycloundecane) and [12]aneS₂Te (1,5-dithia-9-telluracyclododecane), together with polymer. These new small ring macrocycles may be purified by flash column chromatography on silica (11-and 12-membered rings) or by recrystallisation from MeOH–thf (9-membered ring), affording yellow waxy solids. The products have been characterised by NMR (¹H, ¹³C{¹H} and ¹²⁵Te{¹H}) and IR spectroscopy, mass spectrometry and the crystal structures of [11]aneS₂Te and [12]aneS₂Te have been obtained. The more stable organo-Te(IV) derivatives [n]aneS₂TeI₂ (n = 11 or 12) and [n]aneS₂TeMeI (n = 9, 11 or 12) are obtained in high yield as powdered solids by reaction with I₂ or MeI and these have been characterised similarly. A crystal structure of [12]aneS₂TeI₂ has also been determined and is compared with the parent macrocycle. The synthesis of [9]aneS₂Te is more sensitive to the precise reaction conditions than the others, and is accompanied by the formation of the ring-contraction products 1-thia-4-telluracyclohexane and 1,4-dithiane. These too have been characterised by NMR and IR spectroscopy and by mass spectrometry. The former has been unambiguously identified by X-ray crystallography and its Te(IV) methiodide derivative has been prepared for comparison. The ligating properties of the new dithiatellura-macrocycles have been investigated with a variety of transition metal species giving fac-[Mn(CO)₃(L)]CF₃SO₃, cis-[MCl₂(L)] (M = Pd or Pt), [Rh(Cp*)(L)](PF₆)₂, [Cu(L)]BF₄ and [Ag(L)]CF₃SO₃. Where possible, the mode of coordination has been established by spectroscopic methods, ring-size effects established and the data compared with other complexes incorporating related cyclic and acyclic ligands.