Triaquahexathiocyanatobismuthlanthanum dihydrate, [Bi(SCN)(6)La(H2O)(3)]center dot 2H(2)O, and triaquahexathiocyanatobismuthneodymium dihydrate, [Bi(SCN)(6)Nd(H2O)(3)]center dot 2H(2)O

In the crystal state, the title compounds form dihydrated three-dimensional polymeric complexes of general formula [Bi(SCN)(6)Ln(H2O)(3)].2H(2)O, isomorphic with and with a similar structure to the LaFe(CN)(6).5H(2)O structure type. The distorted octahedral BiS6 polyhedra and LnN(6)O(3) polyhedra are connected by the bridging thiocyanate groups in the three-dimensional network. Six N atoms form trigonal prisms around the Ln(III) ions with the three rectangular faces capped by three H2O molecules. This gives La and Nd coordination polyhedra in the form of tricapped trigonal prisms. The different structural roles of the water molecules explains the literature data regarding a two-stage dehydration of the crystals. A comparison of the bond lengths in the two structures is given.