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‐Trip 2 C 6 H 3 , Trip = 2,4,6‐ i Pr 3 C 6 H 2 ] derived from terphenyl‐substituted thio‐ and selenophenols. In the solid‐state structures of dimeric 2a , 2b , 3a , and 3b additional metal‐η n –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 = C 6 H 4 ‐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)