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 (125)Te MAS NMR spectroscopy and X-ray crystallography and in solution by multinuclear NMR spectroscopy ((1)H, (13)C, (125)Te), 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.

Synthesis and structure of diarylhalotelluronium hexahalotellurates [(8-Me2 NC10 H6)2 TeX]2 TeX6 (X=Cl, Br)

“…Overall, these parameters are very similar to those of [(8-Me 2 NC 10 H 6 ) 2 TeX]X (X = Cl, Br) (Beckmann et al, 2013). Besides the first coordination sphere, there is a secondary contact arising from ion pairing.…”

“…Besides the first coordination sphere, there is a secondary contact arising from ion pairing. The related Te1···Cl2 [3.291(2) Å] and Te1···Br2 [3.570(2) Å] bond distances of 1 and 2 are slightly longer than those of [(8-Me 2 NC 10 H 6 ) 2 TeX]X [X = Cl: 3.173(1) Å; X = Br: 3.411(4) Å] (Beckmann et al, 2013). Thus, considering also the second coordination sphere, the spatial arrangement of the Te (14), C10-Te1-C20 97.2(2); ion contact: Te1···Cl2 3.291(2).…”

“…Recently, we reported on a series of diaryltelluronium compounds [(8-Me 2 NC 10 H 6 ) 2 TeX]Y (X = Cl, Br, I, OH; Y = Cl, Br, I, I 3 , PF 6 , O 3 SCF 3 ) in which two intramolecularly coordinating 8-dimethylaminonaphthyl substituents gave rise to cationic structures (Beckmann et al, 2012(Beckmann et al, , 2013.…”

“…After their structural elucidation, the same products were deliberately prepared in good yields by the reaction of analytically pure (8-Me 2 NC 10 H 6 ) 2 Te with SO 2 Cl 2 and Br 2 , respectively, followed by the immediate addition of TeCl 4 and TeBr 4 , respectively (Scheme 1). The last two apparently abstract chloride and bromide ions from the initially formed diarylhalotelluronium halides [(8-Me 2 NC 10 H 6 ) 2 TeX]X (X = Cl, Br) (Beckmann et al, 2013).…”

“…The title compounds [(8-Me 2 NC 10 H 6 ) 2 TeX] 2 TeX 6 (1, X = Cl; 2, X = Br) were obtained as yellow and brown single crystals that were substantially more stable than the initial oxidation products [(8-Me 2 NC 10 H 6 ) 2 TeX]X (X = Cl, Br) (Beckmann et al, 2013). The molecular structures of 1 and 2 are shown in Figures 1 and 2, respectively.…”