Selone-stabilized aryltellurenyl cations

Abstract

Selone (L) causes cleavage of the Te–Te bond of RTe(Br) ₂TeR (R = 2,6-Me ₂Ph) to give the first selone adduct of the 2,6-dimethylphenyltellurenyl cation with the 2,6-dimethylphenyltellurium dibromide anion, [(2,6-Me ₂C ₆H ₃)Te(L)] ⁺[(2,6-Me ₂C ₆H ₃)TeBr ₂] ⁻.

Abstract

Controlled bromination of a diarylditelluride, R ₂Te ₂ (R = 2,6-dimethylphenyl) ( 6) in dichloromethane led to the formation of a Te ^II–Te ^IV mixed-valent tellurenyl bromide, RBr ₂TeTeR ( 7). A further reaction of 7 with 1,3-dibutylbenzimidazolin-2-selone, C ₁₅H ₂₂N ₂Se (L) ( 9), produced the first selone adduct of the 2,6-dimethylphenyltellurenyl cation with the 2,6-dimethylphenyltellurium dibromide anion, [(2,6-Me ₂C ₆H ₃)Te(L)] ⁺[(2,6-Me ₂C ₆H ₃)TeBr ₂] ⁻ ( 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-Me ₂C ₆H ₃)Te(L)Br] ( 11b) and bis(2,6-dimethylphenyl)tellurium dibromide, [(2,6-Me ₂C ₆H ₃) ₂TeBr ₂], ( 13). The metathesis reaction of 11b with AgBF ₄ produced a stable dark red colored selone adduct of the 2,6-dimethylphenyltellurenyl cation with the BF ₄ ⁻ anion, [(2,6-Me ₂C ₆H ₃)Te(L)] ⁺BF ₄ ⁻ ( 15). The selone adducts of aryltellurenyl halides, i.e. [(2,6-Me ₂C ₆H ₃)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, C ₁₅H ₂₂N ₂SeX ₂ ( 14a–14c). Triphenylphosphine (PPh ₃), when treated with [(2,6-Me ₂C ₆H ₃)Te(L)X] ( 11a–11c), substitutes selone from the adduct to afford the triphenylphosphine adducts of aryltellurenyl halides, [(2,6-Me ₂C ₆H ₃)Te(PPh ₃)X] ( 16a–16c).