Triaquahexathiocyanatobismuthlanthanum Dihydrate, [Bi(SCN)₆La(H₂O)₃].2H₂O, and Triaquahexathiocyanatobismuthneodymium Dihydrate, [Bi(SCN)₆Nd(H₂O)₃].2H₂O

In the crystal state, the title compounds form dihydrated three-dimensional polymeric complexes of general formula [Bi(SCN)₆Ln(H₂O)₃].2H₂O which are isomorphic and similar to the LaFe(CN)₆.5H₂O type. The distorted octahedral BiS₆ polyhedra and LnN₆O₃ 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 about two-stage dehydration of the crystals. A comparison of the bond lengths in both structures is given.

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