Selenocyanates, metal

Selenium(IV) oxychloride, 3 130 Selenium (II) xanthates, 4 91 Selenocyanates, metal, 2 186, 188 Shaking apparatus, for keeping... 

A number of compounds of the types RBiY2 or R2BiY, where Y is an anionic group other than halogen, have been prepared by the reaction of a dihalo- or halobismuthine with a lithium, sodium, potassium, ammonium, silver, or lead alkoxide (120,121), amide (122,123), a2ide (124,125), carboxylate (121,126), cyanide (125,127), dithiocarbamate (128,129), mercaptide (130,131), nitrate (108), phenoxide (120), selenocyanate (125), silanolate (132), thiocyanate (125,127), or xanthate (133). Dialkyl- and diaryUialobismuthines can also be readily converted to secondary bismuthides by treatment with an alkali metal (50,105,134) ... 

Pseudohalides of Se in which the role of halogen is played by cyanide, thiocyanate or selenocyanate are known and, in the case of Se are much more stable with respect to disproportionation than are the halides themselves. Examples are Se(CN)2, Se2(CN)2, Se(SeCN)2, Se(SCN)2, Se2(SCN)2. The selenocyanate ion SeCN is ambidentate like the thiocyanate ion, etc., p. 325), being capable of ligating to metal centres via either N or Se, as in the osmium(IV) complexes [OsCl5(NCSe)], [OsCl5(SeCN)], and trans-[OsCU(NCSe)(SeCN)]2-.920) Tellurium and polonium pseudohalogen analogues include Te(CN)2 and Po(CN)4 but have been much... 

In recent years research in the field of transition-metal thiocyanates and selenocyanates received a new impetus, because of the partly interesting physical properties of such crystalline species. A review on Cd and Hg thiocyanate systems collects and sorts results of this endeavor.371 The nonlinear optical (NLO) properties of Cd thiocyanate and selenocyanate systems and criteria for the design of NLO crystals (crystal engineering), especially, have been discussed afterwards.372 Further contributions to the field have also been described.37, 374 The structure of mercury chlorothiocyanate has been re-determined.375... 

However, selenium and tellurium do not react with hydrogen, so the hydrogen compounds are prepared by reacting the elements with a metal, then treating it with an acid. Selenium and tellurium undergo addition reactions with cyanides to yield selenocyanates and tellurocyanates ... 

Zinc Selenocyanate may be obtained by dissolving either the metal or its oxide in selenocyanie acid. It forms groups of prismatic needles, which are not deliquescent.4 By the action of selenium on a solution of zinc cyanide in liquid ammonia, the compound Zn(CNSe)a. 4NIT8 has been obtained.5 Similar compounds of magnesium and aluminium have also been described. 

Selenocyanates, M1 SeCN, corresponding to the thiocyanates, are prepared by addition of selenium to soluble cyanides. They are similar to the thiocyanates except that HSeCN immediately decomposes in acid to selenium and hydrogen cyanide. The heavy metal selenocyanates are less soluble than the corresponding thiocyanates,... 

These results explain previous observations of the greater stability of zirconium thiocyanate and selenocyanate complexes compared with their hafnium analogues, and the greater stability of zirconium and hafnium complexes in MeCN compared with DMF in terms of competition between the ligand and solvent molecules for co-ordination sites on the metal. Zirconium alkoxides have been prepared from ZrCl4 and aliphatic alcohols158 but with salicylaldehyde a Meerwein-Ponndorf... 

Various reducing agents have been used for the generation of selenolates from diselenides or selenocyanates. Alkali metals M (M = Li, Na, K)149,150 or alkali hydrides MH (M = Li, Na, K)151,152 can generate the corresponding selenolate anions such as 80 these are more reactive than the borane complexes of type 77 (Scheme 15). Diaryl diselenides are easier reduced than dialkyl diselenides, but the mechanism for the reduction of selenocyanates is complex and can lead to either diselenides or selenolates.153,154... 

Table XLI summarizes the structures of known, homogeneous, anionic selenocyanate complexes. Although fewer examples exist than for the corresponding thiocyanate complexes, it is apparent that a similar pattern exists for the two sets of complexes. Class a metals are coordinated by the nitrogen atom, whereas selenium is the donor for the class b metals. In mixed metal complexes containing bridging seleno-oyanate groups the nitrogen atom coordinates to the harder or class a metal, and the selenium atom bonds to the softer or class b metal, as was observed with the corresponding thiocyanate complexes.

The preceding sections have shown that the behavior of the thiocyanate and selenocyanate groups in homogeneous complex anions is identical in both cases the nitrogen atom coordinates to the class a metal, and the sulfur or selenium atoms coordinate to the class b metal. Although fewer comparable cyanate complexes are known, it is quite clear that the coordination of the cyanate group is not governed by the same factors. 

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