Diarylhalotelluronium(iv) cations [(8-Me2NC10H6)2TeX]+ (X = Cl, Br, I) stabilized by intramolecularly coordinating N-donor substituents

Abstract

The stoichiometrically controlled halogenation of the intramolecularly coordinated diaryltelluride (8-Me₂NC₁₀H₆)₂Te using SO₂Cl₂, Br₂ and I₂ was studied. At an equimolar ratio, the diarylhalotelluronium cations [(8-Me₂NC₁₀H₆)₂TeX]⁺ (1, X = Cl; 2, X = Br; 3, X = I) formed and were isolated as 1·Cl⁻·H₂O·1/2THF, 2·Br⁻, and 3·I⁻, respectively. When the same reactions were carried out in the presence of KPF₆, 1·PF₆⁻ and 2₂·Br⁻·PF₆⁻ were obtained. The chlorination of (8-Me₂NC₁₀H₆)₂Te with an excess of SO₂Cl₂ occurred with a double electrophilic substitution at the 8-dimethylaminonaphthyl residues (in the ortho- and para-positions) and afforded the diaryltellurium dichloride (5,7-Cl₂-8-Me₂NC₁₀H₄)₂TeCl₂ (4). The bromination of (8-Me₂NC₁₀H₆)₂Te with three equivalents of Br₂ took place with a single electrophilic substitution at the 8-dimethylaminonaphthyl residues (in the para-positions) and provided the diaryltellurium dibromide (5-Br-8-Me₂NC₁₀H₅)₂TeBr₂ (5), while an excess of Br₂ produced the diarylbromotelluronium cation [(5-Br-8-Me₂NC₁₀H₅)₂TeBr]⁺ (6) that was isolated as 6·Br₃⁻. The reaction of (8-Me₂NC₁₀H₆)₂Te with two or three equivalents of iodine provided 3·I₃⁻ and 3·I₃⁻·I₂, respectively. In the presence of water, 1·Cl⁻·H₂O·1/2THF, 2·Br⁻, 3·I⁻ and 3·I₃⁻ hydrolyzed to give the previously known diarylhydroxytelluronium cation [(8-Me₂NC₁₀H₆)₂TeOH]⁺ (7) that was isolated as 7·Cl⁻, 7·Br⁻·H₂O·THF, 7·I⁻ and 7·I₃⁻·H₂O, respectively. The molecular structures of 1–7 were investigated in the solid-state by ¹²⁵Te MAS NMR spectroscopy and X-ray crystallography and in solution by multinuclear NMR spectroscopy (¹H, ¹³C, ¹²⁵Te), electrospray mass spectrometry and conductivity measurements. The stabilization of cations 1–3 by the intramolecular coordination was estimated by DFT calculations at the B3PW91/TZ level of theory.