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

The reaction of Na2Te with various (alpha),(omega)-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.