catena-Poly[[bis­(μ(2)-1,4,7,10,13,16-hexa­oxacyclo­octa­deca­ne)dipotassium]-μ(2)-iodido-(iodidocadmium)-di-μ(2)-iodido-(iodidocadmium)-μ(2)-iodido]

The reaction of CdCl(2), 18-crown-6 and KI in water yields the title coordination polymer, [{K(C(12)H(24)O(6))}(2)Cd(2)I(6)](n). The potassium ion lies approximately in the plane of the crown ether, coordinated by all six crown ether O atoms and also by an iodide anion bound to a cadmium atom. A C atom of the crown ether is disordered over two positions with site occupancies of 0.77 (2) and 0.23 (2). Two K(18-crown-6)(+) units are linked by inversion symmetry, forming a [bis­(μ(2)-18-crown-6)dipottasium] system with approximately square-planar K(2)O(2) units. Inversion symmetry also generates the Cd(2)I(6) fragment and the polymeric system is extended along the c axis by the formation of K—I—Cd bridges.