Synthesis and complexation of the mixed tellurium–oxygen macrocycles1-tellura-4,7-dioxacyclononane, [9]aneO2Te, and 1,10-ditellura-4,7,13,16-tetraoxacyclooctadecane, [18]aneO4Te2 and their selenium analogues

Abstract

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.