Alkali metal complexes of bis-o-xylyl-(17-crown-5): from a dinuclear monomer and a dinuclear polymer to sandwich polymer

Herein, alkali metal complexes of bis-o-xylyl-(17-crown-5) (L) with different binding modes are reported. When NaI was reacted with L, a disodium(I) complex of the type [Na-2(L)(H2O)(2)]I-2 (1) with a good fit mode was isolated, providing the crown unit as a base of the pentagonal pyramid and a water molecule at its apex. However, the use of KPF6 gave a one dimensional (1-D) coordination polymer of type [K-2(L)(PF6)(2)](n) (2), in which dipotassium(I) complex units with a perching mode are linked by two PF6- ions to form an infinite zigzag chain. A cesium(I) ion is large enough to bind two crown units from different ligands with a sandwich mode to give a 1-D sandwich polymer of the type {[Cs(L)]Cl}(n) (3) as a first example, which might be applied as a networking tool in crystal engineering.