DIPHENYLTELLURIUM(IV) BIS(DIORGANOPHOSPHINODITHIOATES) - X-RAY CRYSTAL-STRUCTURE OF PH(2)TE(S2PPH2)(2)CENTER-DOT-0.5CHCL(3) AND A MULTINUCLEAR NMR-STUDY OF THE DECOMPOSITION PROCESS OF PH(2)TE(S(2)PR(2))(2) TOPH(2)TE-II AND [R(2)P(S)S](2)

New diorganophosphinodithioato derivatives, Ph(2)Te(S(2)PR(2))(2), wer e formed in the reaction of Ph(2)TeCl(2) with R(2)PS(2)M . xH(2)O (R = Me, Et, M = Na, x = 2; R = Ph, M = NH4, x = 0) in a 1:2 molar ratio. In the case of alkyl derivatives, the expected Te-IV compounds decompo sed rapidly to Ph(2)Te(II) and the corresponding disulphane, R(2)P(S)- S-S-(S)PR(2), as proved by multinuclear (H-1, C-13, P-31) NMR studies. By contrast, for R = Ph the desired tellurium compound could be isola ted as a pure sample and its crystal and molecular structure has been determined by single-crystal X-ray diffractometry. The 1,1-dithio liga nds are coordinated to tellurium as anisobidentate groups, with single P-S [2.081(2), 2.057(2) Angstrom] and double P=S [1.954(2), 1.966(2) Angstrom] bonds coupled with primary Te-S [2.597(2), 2.658(2) Angstrom ] bonds and intramolecular Te...S (3.316, 3.286 Angstrom) secondary in teractions, respectively. If only the primary covalent bonds are consi dered the coordination geometry about the central tellurium atom can b e described as psi-trigonal bipyramidal, with two sulphur atoms in axi al positions [S(1)-Te(1)-S(3) 174.1(1)degrees]. Two carbon atoms and t he stereochemical active lone electron pair of tellurium occupy the eq uatorial sites. If the secondary interactions of tellurium with the S( 2) and S(4) atoms which are placed above and below the C2Te equatorial plane are taken into account the coordination number at tellurium is increased to 7 (including the lone pair).