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In methyl thiocyanate, N≡C and C−S distances are 116 and 176 pm. By contrast, N=C and C=S distances are 117 and 158 pm in isothiocyanates. [7] Typical bond angles for C−S−C are 100°. [3] By contrast C−N=C in aryl isothiocyanates is 165°. Again, the thiocyanate isomers are quite different with C−S−C angle near 100°.
[SCN] − is one of the pseudohalides, due to the similarity of its reactions to that of halide ions. Thiocyanate used to be known as rhodanide (from a Greek word for rose) because of the red colour of its complexes with iron. Thiocyanate is produced by the reaction of elemental sulfur or thiosulfate with cyanide: 8 CN − + S 8 → 8 SCN −
By contrast, in methyl thiocyanate, N≡C and C−S distances are 116 and 176 pm. Typical bond angles for C−N=C in aryl isothiocyanates are near 165°. Again, the thiocyanate isomers are quite different with C−S−C angle near 100°. [3] In both isomers the SCN angle approaches 180°.
Thiocyanate complexes are not widely used commercially. Possibly the oldest application of thiocyanate complexes was the use of thiocyanate as a test for ferric ions in aqueous solution. [15] The reverse was also used: testing for the presence of thiocyanate by the addition of ferric salts. The 1:1 complex of thiocyanate and iron is deeply red.
Strontium thiocyanate refers to the salt Sr(SCN) 2.It is a colorless solid. According to X-ray crystallography, it is a coordination polymer.The Sr 2+ ions are each coordinated to eight thiocyanate anions in a distorted square antiprismatic molecular geometry where each square face contains two adjacent S atoms and two adjacent N atoms.
In the yellow-coloured isomer, the nitro ligand is bound through nitrogen. In the red linkage isomer, the nitrito is bound through one oxygen atom. The O-bonded isomer is often written as [Co(NH 3) 5 (ONO)] 2+. Although the existence of the isomers had been known since the late 1800s, only in 1907 was the difference explained. [2]
Calcium thiocyanate refers to the salt Cs(SCN) 2. It is a colorless solid. According to X-ray crystallography, it is a coordination polymer. The Ca 2+ ions are each bonded to eight thiocyanate anions, with four Ca-S and four Ca-N bonds. The motif is reminiscent of the fluorite structure. [1]
One of the thiocyanic acid tautomers, HSCN, is predicted to have a triple bond between carbon and nitrogen. Thiocyanic acid has been observed spectroscopically. [12] The salts and esters of thiocyanic acid are known as thiocyanates. The salts are composed of the thiocyanate ion ([SCN] −) and a suitable cation (e.g., potassium thiocyanate, KSCN).