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

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 [K 2 ( L )](ClO 4 ) 2 · CH 3 CN ( 1 ) as well as a mononuclear complex [K( L )][Pt(tht)Cl 5 ] ( 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 {[Ag 2 ( L )(ClO 4 ) 2 ] · CH 2 Cl 2 } n ( 3 ) was obtained, while silver(I) nitrate afforded a 2‐D coordination polymer {[Ag 2 ( L )(µ‐NO 3 ) 2 ] · CH 3 OH} 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.