Synthesis and Characterization of Hypervalent OrganotelluriumAnion Species

近年来，人们对高价有机醇化合物进行了大量的研究，因为硫族化合物具有两个可接近的较高氧化态(IV和VI)，这两个状态可以形成各种潜在的化合物。然而，对于价为VI的硫族化合物的研究很少，直到我们最近报道了六芳基碲Ar6Te作为中性化合物Te^&lt；VI&gt；的合成，才被描述为六芳基硫族化合物。此外，我们还报道了五苯基碲(Ph_5Te~(2+))的合成和表征。虽然相应的阴离子物种Ph_5Te^-被报道为Ph_4Te与PhLi反应的不稳定中间体，但分离的高价碲化合物一直是缺失的一类化合物。本文首次分离得到高价有机碲阴离子Ph_5Te^-Li^+(DME)_3，并对其结构进行了表征，合成了Ph_5Te^-Li^+(DME)_3。将混合物的溶剂交换为二甲醚后，得到黄色橙色固体Ph_5Te^-Li^+(DME)_3。所有操作均在-78℃下进行。以二甲醚为原料在低温下生长了单晶，并在-160℃下进行了X射线单晶分析。分子结构表明，Ph_5Te^-具有围绕碲的四方锥体(拟八面体)结构和Te-C(基础)键长(2.329-2)。342A)比尖端Te-C键长(2.153Å)。分离的高价阴离子在-30℃的固态下相对稳定。碲离子分别与CH3I或SO2Cl2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.