Hypervalent adducts of chalcogen-containing peri-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][E0R] (ER/E0R = 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.