Selenocyanates

The advantage of this method is that it avoids the use of hydrogen selenide, necessary for the preparation of selenourea from cyanamide (14). Benzoylselenourea is synthesized by the method of Douglass (24) by the action of potassium selenocyanate On benzoyl chloride in acetone solution. 

Amino-A.-selenazoline and its 5-methyl derivative have previously been obtained by Baringer (61) starting from 2-bromoethylamine hydrobromide and l-amino-2-bromopropane hydrobromide, respectively, by reaction with potassium selenocyanate. 

Thousands of compounds of the actinide elements have been prepared, and the properties of some of the important binary compounds are summarized in Table 8 (13,17,18,22). The binary compounds with carbon, boron, nitrogen, siUcon, and sulfur are not included these are of interest, however, because of their stabiUty at high temperatures. A large number of ternary compounds, including numerous oxyhaUdes, and more compHcated compounds have been synthesized and characterized. These include many intermediate (nonstoichiometric) oxides, and besides the nitrates, sulfates, peroxides, and carbonates, compounds such as phosphates, arsenates, cyanides, cyanates, thiocyanates, selenocyanates, sulfites, selenates, selenites, teUurates, tellurites, selenides, and teUurides. 

The contributions from the canonical forms have been calculated, and the contributions from the equivalent polar stmctures (2) and (3) dominate those of (4) and (5) (6). Thus, electrophilic substitution is predicted to occur in the a-position, and this is proven experimentally in most cases. Nitrosation and selenocyanation occur at the P-position (7,8). 

Other inorganic selenium compounds include sodium selenocyanate [4768-87-0], NaSeCN, which is prepared by melting together selenium and sodium cyanide selenocyanogen [27151 -67-3] (SeCN)2 sodium selenosulfate [25468-09-1], Na2SeS02, which is prepared by dissolving selenium in aqueous sodium sulfite (acidification decomposes this compound) and selenate alums, eg, Al2(Se0 2 I SeO [13530-59-1]. 

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) ... 

A related ring closure is also successful in the thiazole series. Treatment of a /3-amino-a,/3-unsaturated ketone with thiocyanogen gave the intermediate thiocyano compound (323) which underwent ring closure to the 2-iminothiazoline derivative (324) (83MI40300). Related reactions are described in Chapter 4.19, and for those involving potassium selenocyanate see Chapter 4.20. 

Thiocyanates and selenocyanates can be made by fusing the corresponding cyanide with S or Se. The SCN and SeCN ions are both linear, like OCN . (See p, 779 for TeCN ) Treatment of KSCN with dry KHSO4 produces free isothiocyanic acid HNCS, a white crystalline solid which is stable below 0° but which decomposes rapidly at room temperatures to HCN and a yellow solid H2C2N2S3. Thiocyanic acid, HSCN, (like HOCN) has not been prepared... 

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... 

Selen-verbindung, /. selenium compound, -wasserstoff, m, hydrogen selenide. -was-serstoffsaure, /. hydroselenic acid, -wismut-glanz, m. guanajuatite. -zelle, /. selenium cell, -zyanid, n. selenium cyanide seleno cyanate. -zyankalium, n. potassium selenocyanate. 

Coordination chemistry of cyanate, thiocyanate and selenocyanate ions. A. H. Norbury, Adv. Inorg. Chem. Radiochem., 1975,17,232-386 (825). 

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