Selone-stabilized aryltellurenyl cations

Abstract

Controlled bromination of a diarylditelluride, R₂Te₂ (R = 2,6-dimethylphenyl) (6) in dichloromethane led to the formation of a Te^II–Te^IV mixed-valent tellurenyl bromide, RBr₂TeTeR (7). A further reaction of 7 with 1,3-dibutylbenzimidazolin-2-selone, C₁₅H₂₂N₂Se (L) (9), produced the first selone adduct of the 2,6-dimethylphenyltellurenyl cation with the 2,6-dimethylphenyltellurium dibromide anion, [(2,6-Me₂C₆H₃)Te(L)]⁺[(2,6-Me₂C₆H₃)TeBr₂]⁻ (10). The red colored cationic adduct 10 is not stable in acetonitrile and disproportionated to give the selone adduct of 2,6-dimethylphenyltellurenyl bromide, [(2,6-Me₂C₆H₃)Te(L)Br] (11b) and bis(2,6-dimethylphenyl)tellurium dibromide, [(2,6-Me₂C₆H₃)₂TeBr₂], (13). The metathesis reaction of 11b with AgBF₄ produced a stable dark red colored selone adduct of the 2,6-dimethylphenyltellurenyl cation with the BF₄⁻ anion, [(2,6-Me₂C₆H₃)Te(L)]⁺BF₄⁻ (15). The selone adducts of aryltellurenyl halides, i.e. [(2,6-Me₂C₆H₃)Te(L)X] (X = Cl, Br, I) (11a–11c), have been synthesized by a one-pot reaction of 6 with an equimolar mixture of 9 and 1,3-dibutylbenzimidazolin-2-dihaloselones, C₁₅H₂₂N₂SeX₂ (14a–14c). Triphenylphosphine (PPh₃), when treated with [(2,6-Me₂C₆H₃)Te(L)X] (11a–11c), substitutes selone from the adduct to afford the triphenylphosphine adducts of aryltellurenyl halides, [(2,6-Me₂C₆H₃)Te(PPh₃)X] (16a–16c).