Mesityltellurenyl Cations Stabilized by Triphenylpnictogens [MesTe(EPh₃)]⁺ (E = P, As, Sb)

The homoleptic 1:1 Lewis pair (LP) complex [MesTe­(TeMes₂)]­O₃SCF₃ (<b>1</b>) featuring the cation [MesTe­(TeMes₂)]⁺ (<b>1a</b>) was obtained by the reaction of Mes₂Te with HO₃SCF₃. The reaction of <b>1</b> with Ph₃E (E = P, As, Sb, Bi) proceeded with substitution of Mes₂Te and provided the heteroleptic 1:1 LP complexes [MesTe­(EPh₃)]­O₃SCF₃ (<b>2</b>, E = P; <b>3</b>, E = As) and [MesTe­(SbPh₃)]­[Ph₂Sb­(O₃SCF₃)₂] (<b>4</b>) featuring the cations [MesTe­(EPh₃)]⁺ (<b>2a</b>, E = P; <b>3a</b>, E = As; <b>4a</b>, E = Sb) and the anion [Ph₂Sb­(O₃SCF₃)₂]⁻ (<b>4b</b>). In the reaction with Ph₃Bi, the crude product contained the cation [MesTe­(BiPh₃)]⁺ (<b>5a</b>) and the anion [Ph₂Bi­(O₃SCF₃)₂]⁻ (<b>5b</b>); however, the heteroleptic 1:1 LP complex [MesTe­(BiPh₃)]­[Ph₂Bi­(O₃SCF₃)₂] (<b>5</b>) could not be isolated because of its limited stability. Instead, fractional crystallization furnished a large amount of Ph₂BiO₃SCF₃ (<b>6</b>), which was also obtained by the reaction of Ph₃Bi with HO₃SCF₃. The formation of the anions <b>4b</b> and <b>5b</b> involves a phenyl group migration from Ph₃E (E = Sb, Bi) to the MesTe⁺ cation and afforded MesTePh as the byproduct, which was identified in the mother liquor. The heteroleptic 1:1 LP complexes <b>2</b>–<b>4</b> were also obtained by the one-pot reaction of Mes₂Te, Ph₃E (E = P, As, Sb) and HO₃SCF₃. Compounds <b>1</b>–<b>4</b> and <b>6</b> were investigated by single-crystal X-ray diffraction. The molecular structures of <b>1a</b>–<b>4a</b> were used for density functional theory calculations at the B3PW91/TZ level of theory and studied using natural bond order (NBO) analyses as well as real-space bonding descriptors derived from an atoms-in-molecules (AIM) analysis of the theoretically obtained electron density. Additionally, the electron localizability indicator (ELI-D) and the delocalization index are derived from the corresponding pair density