American Chemical Society
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Redox Chemistry of Tellurium Bis(tert-butylamido)cyclodiphosph(V)azane Disulfide and Diselenide Systems:  A Spectroscopic and Structural Study

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journal contribution
posted on 2002-03-12, 00:00 authored by Glen G. Briand, Tristram Chivers, Gabriele Schatte
The redox chemistry of tellurium−chalcogenide systems is examined via reactions of tellurium(IV) tetrachloride with Li[tBuN(E)P(μ-NtBu)2P(E)N(H)tBu] (3a, E = S; 3b, E = Se). Reaction of TeCl4 with 2 equiv of 3a in THF generates the tellurium(IV) species TeCl3[HcddS2][H2cddS2] 4a [cddS2 = tBuN(S)P(μ-NtBu)2P(S)NtBu] at short reaction times, while reduction to the tellurium(II) complex TeCl2[H2cddS2]2 5a is observed at longer reaction times. The analogous reaction of TeCl4 and 3b yields only the tellurium(II) complex TeCl2[H2cddSe2]2 5b. The use of 4 equiv of 3a or 3b produces Te[HcddE2]2 (6a (E = S) or 6b (E = Se)). NMR and EPR studies of the 5:1 reaction of 3a and TeCl4 in THF or C6D6 indicate that the formation of the Te(II) complex 6a via decomposition of a Te(IV) precursor occurs via a radical process to generate H2cddS2. Abstraction of hydrogen from THF solvent is proposed to account for the formation of 2a. These results are discussed in the context of known tellurium−sulfur and tellurium−nitrogen redox systems. The X-ray crystal structures of 4a·[C7H8]0.5, 5a, 5b, 6a·[C6H14]0.5, and 6b·[C6H14]0.5 have been determined. The cyclodiphosph(V)azane dichalcogenide ligand chelates the tellurium center in an E,N (E = S, Se) manner in 4a·[C7H8]0.5, 6a·[C6H14]0.5, and 6b·[C6H14]0.5 with long Te−N bond distances in each case. Further, a neutral H2cddS2 ligand weakly coordinates the tellurium center in 4a·[C7H8]0.5 via a single chalcogen atom. A similar monodentate interaction of two neutral ligands with a TeCl2 unit is observed in the case of 5a and 5b, giving a trans square planar arrangement at tellurium.