Structural studies of lithium telluro- and seleno-phosphorus compounds

Lithium tellurophosphinite [Ph2PTe][Li(TMEDA)(1.33)-(THF)(1.33)] (4), ditellurophosphinate, [Ph2PTe2][Li(THF)(3.5)- (TMEDA)(0.25)] (5), and selenotellurophosphinate [Ph2P(Se)Te]-[Li(THF)(2)(TMEDA)] (6) complexes have been prepared from the insertion/oxidation reactions of lithiated secondary phosphanes with elemental chalcogens and characterised by X-ray crystallography. Compounds 4-6 contain no tellurium-lithium bonding interactions in the solid state, instead existing as ion-separated species with THF/TMEDA-solvated lithium cations. Reaction of dilithiated primary phosphanes with more than three equivalents of elemental selenium gives [{(C-C6H11)P(Se)(SeLi)}(2).2TMEDA] (7) via a phosphorus-phosphorus coupling reaction. Solid state characterisation of 7 reveals the organo groups in the tetradentate tetraselenohypodisphosphinate ligand to be in an anti conformation to one another and each lithium atom to be coordinated by two selenium atoms, one from each of the diselenophosphinate groups. Multinuclear NMR spectroscopic data are consistent with retention of the solid-state structures of 4-7 in solution. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003).