Synthesis and complexation of the mixed tellurium–oxygen macrocycles 1-tellura-4,7-dioxacyclononane, [9]aneO 2 Te, and 1,10-ditellura-4,7,13,16-tetraoxacyclooctadecane, [18]aneO 4 Te 2 and their selenium analogues

1,10-Ditellura-4,7,13,16-tetraoxacyclooctadecane ([18]aneO4Te2) has been synthesised in good yield (50–55%) from Na2Te and ClCH2CH2OCH2CH2OCH2CH2Cl in liquid ammonia, and fully characterised by NMR spectroscopy (1H, 13C{1H} and 125Te{1H}) and mass spectrometry, and by the preparation of the Te(IV) derivatives [18]aneO4Te2Me2I2 and [18]aneO4Te2Cl4. A minor by-product (ca. 4%) of the preparation is 1-tellura-4,7-dioxacyclononane ([9]aneO2Te) which has been isolated and similarly characterised. The corresponding reaction of Na2Se with ClCH2CH2OCH2CH2OCH2CH2Cl in liquid ammonia is less satisfactory and gives variable yields of 1,10-diselena-4,7,13,16-tetraoxacyclooctadecane ([18]aneO4Se2), which is better obtained from the same reagents in ethanol solution under high dilution conditions. [18]aneO4Se2 has also been thoroughly characterised spectroscopically. In these reactions the nine-membered ring 1-selena-4,7-dioxacyclononane is generally produced only in trace amounts. A range of complexes of [18]aneO4Te2 (L) in which the ligand behaves only as a Te2 donor has been synthesised, including cis-[MX2L] (M = Pd or Pt, X = Cl or Br), [RhCl2L2]Y (Y = Cl or PF6), [CuL2]BF4, [AgL2]BF4 and [Cu2L][BF4]2. The complexes have been characterised by microanalysis, multinuclear NMR spectroscopy (1H, 125Te{1H}, 195Pt, 63Cu), ES+ mass spectrometry, UV/visible and IR spectroscopy as appropriate. Two complexes of [9]aneO2Te, cis-[MCl2{[9]aneO2Te}2] (M = Pd or Pt) are also reported, together with the selenoether complex [PtCl2{[18]aneO4Se2}]. The X-ray structures of [MCl2{[18]aneO4Te2}] (M = Pt or Pd) and [PtCl2{[18]aneO4Se2}] all reveal cis square planar coordination with no interaction between the metal and the ether oxygens.