Cyanates, OCN

Solubility the cyanates of the alkalis and of the alkaline earths are soluble in water. Those of silver, mercury(I), lead, and copper are insoluble. The free acid is a colourless liquid with an unpleasant odour it is very unstable. 

To study these reactions use a 0.2m solution of potassium cyanate, KOCN. 

Dilute sulphuric acid vigorous effervescence, due largely to the evolution of carbon dioxide. The free cyanic acid, HOCN, which is liberated initially, is decomposed into carbon dioxide and ammonia, the latter combining with the sulphuric acid present to form ammonium sulphate. A little cyanic acid, however, escapes decomposition and may be recognized in the evolved gas by its penetrating odour. If the resulting solution is warmed with sodium hydroxide, ammonia is evolved (test with mercury(I) nitrate paper). 

Concentrated sulphuric acid the reaction is similar to that with the dilute acid, but is somewhat more vigorous. 

Silver nitrate solution white, curdy precipitate of silver cyanate, AgOCN, soluble in ammonia solution and in dilute nitric acid. The precipitate appears instantaneously, without complex formation (difference from cyanide)  

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Cyanates (OCN-) can be prepared from cyanides by oxidation reactions. For example,... 

The OCN ligand can attach to the XH3 group to form either the cyanate (—OCN) or isocyanate (—NCO) species. Experimental gas-phase geometric structures have been... 

When coordinated in mononuclear complexes, these loos may bind through either end. This has led to the use of the names isocyartfe [-NCG vs. cyanate, -OCN]. etc., to distinguish ihe donor. This usage Is (Sscounged. and the italicized donor symbol, namely. cyanato-O. or cyanalo-A, should be employed. [Sec page A-72.J... 

Sulfuric acid, concentrated and dilute Silver nitrate Copper sulfate-pyridine test Cyanates, OCN Vigorous effervescence, due largely to evolution of carbon dioxide, with concentrated acid producing a more dramatic effect Curdy white precipitate of silver cyanate Lilac-blue precipitate (interference by thiocyanates) reagent is prepared by adding 2 or 3 drops of pyridine to 0.25 M CuS04 solution... 

Fig. 13. Response of the active site copper complex to chemical and physical perturbations. (A) Absorption spectra for the lAGO Cu(II) complex in the absence (—L) and presence (+L) of a coordinating anion, cyanate (OCN ). (B) Absorption spectra for lAGO Cu(II) complex at ambient (300 K, RT) and cryogenic temperatures (200 K, LT).

Thallium(I) forms salts with cyanide (CN ), cyanamide (NCN ), azide (Ns"), cyanate (OCN ), isocyanate (CNO"), thiocyanate (SCN"), and selenocyanate (SeCN ) however, complexes with these hgands, hke the Tl -halide complexes, are very weak. In contrast, the neutral Tl Xs species are not well known, although the Tl -pseudohahde complexes are more or less stable. 

Other sources of data have generally been of much less use for anhar-monic force field studies than high-resolution infrared and microwave measurements. Solid-state infrared measurements using the matrix-isolation technique have recently provided useful vibrational data for some species inaccessible to gas-phase measurements, e.g., the cyanate (OCN )14 ls and nitrate (NO3)16 anions. Gas-phase Raman measurements of vibration/rotation bands are very difficult to perform with adequate resolution, and Raman data have mainly been utilized for locating some of the infrared-inactive fundamentals in symmetrical molecules such as C02, CS2,17 C2H2,18 CH4,19 20 C. 21"23 High-resolu-... 

Before leaving the topic of the halides, a brief mention of the so-called pseudohalides is in order. These anions resemble halides in their chemical behavior and generally include azide, N cyanide, CN cyanate, OCN thiocyanate, SCN selenocyanate, SeCN and teUurocyanate,TeCN . The similarities between these ions and ordinary halides are remarkable. These include (1) the existence of 1— ions with electronegativities (when averaged over all the atoms in the anion) similar to that of the haUdes, (2) the formation of volatile dimeric molecules that react with metals to make salts, (3) the abUity of these dimeric molecules to serve as oxidizing agents, (4) the ability of HX compounds to serve as acids in aqueous solution,... 

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