Thiacalix[4]‐bis‐crown with Hard Cavities and Soft Bridges Exhibiting Endocyclic Potassium(I) Complexes and Exocyclic Silver(I) Coordination Polymers

Abstract

Thiacalix[4]‐bis‐crown‐5 (L) was employed as a model host molecule, which shows both HSAB concept and endo/exo‐coordination modes. In the K+ complexations, a dinuclear complex [K2(L)](ClO4)2·CH3CN (1) as well as a mononuclear complex [K(L)][Pt(tht)Cl5] (2) (tht = tetrahydrothiophene) were isolated: the latter as first example in such symmetrical hosts. Each K+ in both species is stabilized not only by K+–O bondings (hard acid – hard base) in the crown cavities (endo‐coordination) but also by K+‐π interactions. The Ag+ complexations afforded infinite products (3 and 4) in which the Ag+ binds to the sulphur bridges (soft acid – soft base) from outside the cavity (exo‐coordination). When silver(I) perchlorate was used, a 1‐D coordination polymer {[Ag2(L)(ClO4)2]·CH2Cl2}n (3) was obtained, while silver(I) nitrate afforded a 2‐D coordination polymer {[Ag2(L)(µ‐NO3)2]·CH3OH}n (4). The dimensional difference between 3 and 4 is responsible for the coordination mode of anions where the perchlorate ion and the nitrate ion act as a terminal ligand and a bridging ligand, respectively. The solution studies by NMR titrations indicate the endo‐coordination with K+ and the exo‐coordination with Ag+, similar to those observed in the solid state.