BIS(PYRIDYL)CADMIUM(II) IODIDE COMPLEXES - THERMAL, INCLUSION, AND STRUCTURAL BEHAVIOR

Bis(4-cyanopyridine)cadmium(II) iodide (1) crystallizes as infinite Cd I2 chains, in which cadmium atoms are doubly bridged by pairs of iodin e atoms; 4-cyanopyridine ligands occupy trans positions to complete an octahedral coordination about the cadmium. The chains are associated into layers through self-association of the cyano groups. The layer st ructure of 1 is essentially unchanged as mercury(II) iodide molecules are intercalated between the layers to form 2. Bis(4-vinylpyridine)cad mium(II) iodide (3) crystallizes in a nearly isomorphous fashion with 1; however, lacking a donor site capable of binding to HgI2, it does n ot form an intercalation compound similar to 2. Bis(2-vinylpyridine)ca dmium(II) iodide (4) crystallizes as a molecular species with approxim ate tetrahedral coordination about the four-coordinate cadmium atom; s teric interactions involving the vinyl groups prevent formation of ext ended chains. The 4-vinylpyridine complex undergoes a thermally-induce d solid-state polymerization of the ligand that is not observed in 1, 2 or 4. (C) 1998 Elsevier Science Ltd.