Synthesis and Characterization of Hypervalent OrganotelluriumAnion Species

由于硫原具有两个可接近的高氧化态（IV和VI），可以形成各种电位化合物的特性，近年来人们对高价有机硫原化合物进行了大量的研究。然而，对于那些价态为VI的硫原化合物，我们所知甚少，直到我们最近报道了六芳基碲的合成，Ar6Te，作为含有Te^<VI>的中性化合物，我们才发现六芳基硫原。此外，我们还报道了五苯基碲鎓（Ph_5Te^+）作为高价鎓化合物的合成和表征。虽然在Ph_4Te与PhLi的反应中，已经报道了相应的阴离子Ph_5Te^-是一种不稳定的中间体，但分离的高价碲酸盐化合物一直是缺失的一类化合物。本文首次分离出高价有机碲阴离子Ph_5Te^-Li^+(DME)_3，并分析了其结构。用新制备的Ph_4Te与PhLi反应合成了Ph_5Te^-Li^+(DME)_3。混合物的溶剂由the交换为DME后，得到Ph_5Te^-Li^+(DME)_3为黄橙色固体。所有操作均在-78℃下进行。低温生长二甲醚单晶，-160℃下进行x射线晶体学分析。分子结构表明，Ph_5Te^-在碲周围呈方锥体（伪八面体）结构，Te-C（基底）键长为2。329 - 2。342 A)比顶端Te-C键长(2。153年)。分离得到的高价阴离子在-30℃的固态下相对稳定。碲阴离子与CH_3I或SO_2Cl_2反应，分别得到相应的中性六价有机碲。

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.