| Budget Amount *help |
¥4,190,000 (Direct Cost: ¥3,800,000、Indirect Cost: ¥390,000)
Fiscal Year 2007: ¥1,690,000 (Direct Cost: ¥1,300,000、Indirect Cost: ¥390,000)
Fiscal Year 2006: ¥2,500,000 (Direct Cost: ¥2,500,000)
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| Research Abstract |
Intensive efforts have been recently directed toward the hypervalent organochalcogen compounds because of the peculiarity of chalcogens to have two accessible higher oxidation states (IV and VI) which can form variety of compounds of potential. However, very little is known for those with valence VI chalcogen compounds and no hexaarylated chalcogen had been described until we recently reported the synthesis of hexaaryltellurium, Ar6Te, as neutral compound comprising Te^<VI>. Moreover, we also reported on the synthesis and characterization of pentaphenyltelluronium, Ph_5Te^+, as the hypervalent onium compound. Although corresponding anion species, Ph_5Te^-, has been reported as an unstable intermediate in the reaction of Ph_4Te with PhLi, isolated hypervalent tellurium ate compounds have been the missing class of compound. Here, we present the first isolation of hypervalent organotellurium anion species, Ph_5Te^-Li^+(DME)_3, and its structure.
The synthesis of Ph_5Te^-Li^+(DME)_3 was achieved by the reaction of freshly prepared Ph_4Te with PhLi. After exchange of the solvent from THE to DME of the mixture, Ph_5Te^-Li^+(DME)_3 was obtained as yellow-orange solid. All manipulations were carried out at -78℃. The single crystals were grown from DME at low temperature and X-ray crystallographic analysis was performed at -160℃. The molecular structure indicates that the Ph_5Te^- has square-pyramidal (pseudo octahedral) structure around the tellurium and the Te-C (basal) bond lengths (2. 329-2. 342 A) are longer than the apical Te-C bond length (2. 153Å). The isolated hypervalent anion is relatively stable at -30℃ in the solid state. The reaction of the tellurium anion with CH_3I or SO_2Cl_2 gave corresponding neutral hexavalent organotellurium species, respectively.
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