Reactions of triphenylphosphine and tributylphosphine with tetraethylthiuram disulfide and diethyldithiocarbamate complexes of tellurium(II) and tellurium(IV)

Triphenylphosphine reduces tetrakis(diethyldithiocarbamato)tellurium(IV), TeL4 [L = diethyldithiocarbamate, (C2H5)2NCS-2] to the tellurium(II) complex TeL2, on which PPh3 has no effect. The reaction of the tellurium(IV) complex, TeL2X2 (X = I, Br, Cl) with PPh3 in the molar ratio of 1:1 results in the formation of TeLX, CS2 and an aminophosphonium halide, (C2H5)2NP+Ph3X -. Another mole of PPh3 reduces TeLX further to elemental tellurium. The reactions of TeL3X (X = I, ClO4, PF6) systems with excess PPh3 lead interestingly to the formation of TeL2 and elemental tellurium, with the concomitant formation of CS2, (C2H5)2NEP+Ph3X - and (C2H5)2NC(S)P+Ph3X -. The reactions were performed in dichloromethane solutions and 31P NMR spectroscopy was widely used for the identification of various phosphorus containing species.