Tellurium(II) and tellurium(IV) complexes of phosphine chalcogenide ligands, synthesis and X-ray structures

Reaction of TeX4 (X = Cl or Br) with 2 mol. equiv. of OPR3 (R = Me, Et or Ph) gives the distorted octahedral cis-[TeX4(OPR3)(2)], while the bidentates Ph2P(E)(CH2)(n)P(E)Ph-2 (E = O, n = 1 or 2; E = S, n = 1) give the six-coordinate [TeX4{Ph2P(E)(CH2)(n)P(E)Ph-2}]. These species have been characterised spectroscopically (via H-1 and P-31{H-1} NMR and IR) and by crystallographic analyses on cis-[TeBr4(OPPh3)(2)], [TeCl4{Ph2P(O)CH2-P(O)Ph-2}] and [TeBr4{Ph2P(S)CH2P(S)Ph-2}], The TeX4 (X = Cl or Br) are reduced by Ph2P(S)(CH2)(2)P(S)Ph-2 and Ph2P(Se)CH2P(Se)Ph-2, giving the planar, four-coordinate Te(II) species [Te{Ph2P(S)(CH2)(2)P(S)Ph-2}(2)](2+) (isolated as [(TeCl5)(2){mu-Ph2P(S)(CH2)(2)P(S)Ph-2}](2-) and [TeBr6](2-) salts) and [TeBr2{Ph2P(Se)CH2P(Se)Ph-2}], all of which have also been identified crystallographically. On the basis of the structural data the Te-based lone pair associated with the Te(IV) species is assumed to occupy the 5s orbital, whereas in the Te(II) complexes the planar coordination is consistent with the two stereochemically active lone pairs occupying the axial sites. (C) 2009 Elsevier Ltd. All rights reserved.