Synthesis and Characterization of Hypervalent OrganotelluriumAnion Species

由于硫属元素具有两个可接近的较高氧化态（IV和VI）的特性，这些氧化态可以形成各种潜在的化合物，因此最近已经针对高价有机硫属元素化合物进行了大量的努力。然而，对于具有价VI硫族元素化合物的那些知之甚少，并且直到我们最近报道了六芳基碲Ar 6 Te作为包含Te 2的中性化合物的合成，才描述了六芳基化硫族元素<VI>。此外，我们还报道了五苯基碲鎓（Ph_5Te^+）的合成和表征。在Ph_4Te与PhLi反应中，Ph_5Te^-是一种不稳定的中间体，但尚缺乏高价碲酸盐化合物。本文首次报道了超价有机碲阴离子Ph_5Te^-Li^+（DME）_3的分离和结构，并利用新合成的Ph_4Te与PhLi反应合成了Ph_5Te^-Li^+（DME）_3。将混合物中的溶剂从THE交换为DME后，得到黄橙色固体Ph_5Te^-Li^+（DME）_3。所有操作均在-78℃下进行。在低温下从DME中生长出单晶，并在-160℃下进行了X射线晶体学分析。分子结构表明，Ph_5Te^-以四方锥（拟八面体）结构围绕碲原子，Te-C（基底）键长（2。329-2. 342 A）比顶端Te-C键长（2. 153页）。在-30℃固态下，孤立的高价阴离子相对稳定。碲阴离子分别与CH_3I或SO_2Cl_2反应生成相应的中性六价有机碲物种。

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.