Isostructural Potassium and Thallium Salts of Sterically Crowded Thio‐ and Selenophenols: A Structural and Computational Study

Because of their similar cationic radii, potassium and thallium(I) compounds are usually regarded as closely related. Homologous molecular species containing either K+ or Tl+ are very rare, however. We have synthesized potassium and thallium salts MEAr* [M, E = K, S (2a); K, Se (2b); Tl, S (3a); Tl, Se (3b); Ar* = 2,6‐Trip2C6H3, Trip = 2,4,6‐iPr3C6H2] derived from terphenyl‐substituted thio‐ and selenophenols. In the solid‐state structures of dimeric 2a, 2b, 3a, and 3b additional metal‐ηn–π‐arene interactions to the flanking arms of the terphenyl substituents of different hapticity n are observed. Remarkably, the homologous potassium and thallium complexes 2b and 3b crystallize in isomorphous cells. For 2a, 3a, and model complexes of the composition METph (Tph = C6H4‐2‐Trip) the nature of the M–E and M···C(arene) bonding was studied by density functional theory calculations.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) Sterically crowded, thio‐ and selenophenolate ligands have been used to stabilize dimeric, unsolvated complexes of potassium and thallium. The different nature of the M–E and M···C(arene) bonding was studied by density functional theory calculations that show a higher degree of covalence for the thallium compounds and no significant influence from the lone pair on Tl.