OCTAHEDRAL COORDINATION-COMPLEXES OF TELLURIUM TETRACHLORIDE

The reaction between TeCl4 and two equivalents of OPPh(3) affords crystals of the coordination complex [TeCl4(OPPh(3))(2)], which has been characterized by X-ray crystallography. The coordination geometry around the tellurium centre is close to regular octahedral, with little evidence of any lone pair stereochemical activity, and the oxygen donor atoms are cis. A similar reaction involving the chelating ligand dppmS(2) [Ph(2)P(S)CH2P(S)Ph(2)] afforded the complex [TeCl4(dppmS(2))], which was also characterized by X-ray crystallography and found to be similar in most respects to the OPPh, complex. However, large thermal ellipsoids associated with the two chlorines trans to the sulphur atoms are interpreted in terms of the onset of lone pair stereochemical activity. Attempted preparations of a 4-picoline adduct of TeCl4 and an SPPh(3) adduct of SeCl4 resulted in the complexes [4-picolinium](2)[TeCl6] and [Ph(3)PSH](2)[Se2Cl6] respectively, both of which were characterized by X-ray crystallography.