Hypervalent Adducts of Chalcogen-Containing <i>peri</i>-Substituted Naphthalenes; Reactions of Sulfur, Selenium, and Tellurium with Dihalogens

A range of structurally diverse compounds 1−15 {Nap[SPh]2·Br4 (Nap = naphthalene-1,8-diyl); Nap[SePh][EPh]·Br4 (E = Se, S); Nap[SePh]2·I2; Nap[SePh][EPh]·3/2I2 (E = Se, S); Nap[TePh][G]·X2 (G = SePh, SPh, Br, I; X = Br, I); and [Nap(PPh2OH)(SPh)]+Br3−} formed from the reactions between peri-substituted naphthalene chalcogen donors D1−D8 {Nap[ER][E′R] (ER/E′R = SPh, SePh, TePh); Nap[TePh][X] (X = Br, I); and Nap[PPh2][SPh]} and dibromine and diiodine were characterized by X-ray crystallography and where possible by multinuclear NMR, IR, and MS. X-ray data for 1−15 were analyzed by naphthalene ring torsions, peri-atom displacement, splay angle magnitude, peri-distance, aromatic ring orientations, and quasi-linear three-body arrangements. The hypervalent linear moieties are considered in the context of the charge-transfer model and the 3c−4e model introduced by Pimentel and Rundle. In general, the conformation of the final products obeyed the rule based on charge-transfer that “seesaw” (X−ER2−X, 10-E-4) adducts arise when the halogen (X) is more electronegative than the chalcogen (E), and if the converse is true then, CT “spoke” (X−X−ER2, 8-E-3) adducts are formed. Upon treatment with dibromine, selenium donor compounds D2 {Nap[SePh]2} and D3 {Nap[SePh][SPh]} afford unusual tribromide salts of bromoselenyl cations containing a hypervalent X−E···E′ 3c-4e type interaction. Upon treatment with diiodine, D2 and D3 form “Z-shaped”, “extended spoke” adducts containing an uncommon 2:3 donor/chalcogen ratio and incorporating chains of I2 held together by rare I···I interactions. As expected, “seesaw” 10-E-4 adducts are formed following the reaction of Te donors D4−D7 {Nap[TePh][X] (X = Br, I); Nap[TePh][EPh] (E = Se, S)} with the dihalogens. Naphthalene distortion in general is comparable between respective donor compounds and products 1−15. Ionic species 2 and 3 display a noticeable reduction in molecular distortion explained by the relief of steric strain via weak peri-interactions and the onset of 3c−4e bonding.一系列结构各异的化合物1~15，包括Nap[SPh]₂·Br₄（其中Nap=萘-1,8-二基（naphthalene-1,8-diyl)）、Nap[SePh][EPh]·Br₄（E=Se、S）、Nap[SePh]₂·I₂、Nap[SePh][EPh]·3/2I₂（E=Se、S）、Nap[TePh][G]·X₂（G=SePh、SPh、Br、I；X=Br、I）以及[Nap(PPh₂OH)(SPh)]⁺Br₃⁻。该系列化合物由peri-取代萘基硫族给体（peri-substituted naphthalene chalcogen donor）D1~D8（其中Nap[ER][E′R]的ER/E′R=SPh、SePh、TePh；Nap[TePh][X]的X=Br、I；Nap[PPh₂][SPh]）分别与二溴、二碘反应制得，通过X射线晶体学（X-ray crystallography）进行表征，条件允许时辅以多核核磁共振（multinuclear NMR）、红外光谱（IR）及质谱（MS）完成分析。 针对化合物1~15的X射线衍射数据，我们从萘环扭转角、peri-原子位移、张开角大小、peri-原子间距、芳环取向及准线性三体排布等维度进行解析。本研究结合电荷转移模型与皮门特尔（Pimentel）、伦德尔（Rundle）提出的3中心4电子（3c-4e）模型（3c−4e model），对超价线性结构单元展开讨论。 总体而言，最终产物的构象遵循电荷转移相关规律：当卤素（X）电负性高于硫族元素（E）时，会生成跷跷板型（seesaw）X-ER₂-X（10-E-4）加合物；反之则形成电荷转移（CT）型辐条（spoke）X-X-ER₂（8-E-3）加合物。 以二溴为反应物时，硒基给体化合物D2{Nap[SePh]₂}与D3{Nap[SePh][SPh]}可得到罕见的溴硒阳离子（bromoselenyl cations）三溴化物盐（tribromide salts），该盐中存在X-E···E'型超价3中心4电子相互作用。以二碘为反应物时，D2与D3则形成"Z型""延展辐条型"加合物，此类加合物拥有罕见的给体/硫族元素比例为2:3的组成，并包含由稀有I···I相互作用维系的I₂链结构。 正如预期，碲基给体D4~D7（其中Nap[TePh][X]的X=Br、I；Nap[TePh][EPh]的E=Se、S）与二卤化物反应后，均生成跷跷板型10-E-4加合物。 总体而言，对应给体化合物与产物1~15之间的萘环畸变程度基本相当。离子型物种2与3的分子畸变程度显著降低，该现象可通过弱peri-相互作用缓解空间位阻应变（steric strain）以及3中心4电子成键的形成得到合理解释。