Selenium ligands selenocyanates

K(18-crown-6)]2K[Bi(SCN)6], which exists in two isomeric forms." In the yellow form, octahedral [Bi(SCN)6] " anions are surrounded by four K[K(18-crown-6)]2 units in a layered arrangement all the thiocyanates are A -bound to potassium. In the yellow form, the thiocyanatobismuth anions have four 5-bonded and two trans Ai-bonded thiocyanate ligands, and are arranged in parallel columns separated by K+ cations each potassium has two trans 5-bound and four Ai-bound thiocyanate ligands. Two [K(18-crown-6)] units are located between the columns." Structurally characterized selenocyanate complexes of the i-block metals are much rarer, but as befits the softer nature of selenium relative to sulfur, all known examples are Ai-bound." " " ... 

There are no examples of xenon bonded to sulfur or selenium and few for the halogens. The reported compounds involve the thiocyanate and selenocyanate ligands acting as pseudohalides, in the anions I(SCN)i and I(SeCN)2, for which IR and Raman spectra show the thiocyanate to have a linear S—I—S arrangement but give no definitive results for the selenocyanate, and two examples with more complex thio ligands for which crystal structures have been determined. 

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