AZIDE COMPLEXES OF COBALT

See AZIDE COMPLEXES of cobalt(IH) See related metal azides... 

ACYL AZIDES, AMMINECOB ALT (III) AZIDES, AZIDE COMPLEXES OF COBALT(III)... 

On adding an excess of sodium azide to neutral or slightly acid solutions of cobalt salts, a violet color appears which is due to complex cobalt -azide anions. In contact with air an oxidation to anionic azide-complexes of tervalent cobalt takes place, shown by a change of color from violet to yellow. This very slow autoxidation is enormously accelerated by sulfurous acid or sulfite ions. Probably the autoxidation of sulfite to sulfate induces the oxidation of the complex bounded cobalt. However, the color change violet yellow is not sufficiently sensitive to serve as a test for this induction effect and therefore, for sulfite. It is better to identify the tervalent cobalt through a color reaction with an acetic acid solution of o-tolidine (formation of a blue quinoidal oxidation product of the base). Compare page 209. 

Complex 165 reacts with CO at room temperature to give />-tolyl isocyanate and the golden dicarbonyl compound 166. The latter can also be generated by reaction of 164 with excess of CO and converted back to imide 165 by the addition of 2 equiv of /> toly 1 azide (2003JA322). Reaction of cobalt(m) imide 167 analogous to 165, available from [PhB(CH2PPh2)3]CoI 156 by the same procedure as for 165, with CO proceeds similarly <2002JA11238>. 

A series of 12 complexes of Co(III) with both ionic and covalent azide groups was prepared and most were easily detonable as dry salts, especially at elevated temperatures [1]. Polarography is an accurate and safe method of analysis for azides [2], Hexaammine-cobalt, -chromium and -rhodium hexaazidocobaltates are explosive, particularly in the dry state [3],... 

When acido groups, halides, thiocyanate, azide, acetate, and nitrate are present in the coordination sphere of cobalt(III), they appear to be oxidized in preference to coordinated ammonia. Many of the radicals thus produced are capable of oxidizing ammonia released from the complex or of interfering in other ways with the reduction process, and these systems have proved very difficult to understand even in general terms. Quantum yield and other data for a number of acidopentammine and certain other complexes are given in Table IV the data on the aquation reactions of some of the complexes are considered in Section I1I-D. 

The formation of complexes of l,2,3,4-thiatriazole-5-thiol has been well described in CHEC-II(1996) 1,2,3,4-thiatriazole-5-thiol can form complexes with various metals such as palladium, nickel, platinum, cobalt, zinc, etc. <1996CHEC-II(4)691>. These complexes can be prepared either by cycloaddition reactions of carbon disulfide with metal complexes of azide anion (Equation 20) or directly from the sodium salt of l,2,3,4-thiatriazole-5-thiol with metal salts. For instance, the palladium-thiatriazole complex 179 can be obtained as shown in Equation (20) or it may be formed from palladium(ll) nitrate, triphenylphosphine, and sodium thiatriazolate-5-thiolate. It should be noted that complexes of azide ion react with carbon disulfide much faster than sodium azide itself. 

Cobalt Azide Complexes — Curtius Rissom (Ref 1) found that potassium cobaltoazoimide, [KNj-CofNjl ], pptd when strong solns of the two azides were mixed. This compd appeared as bright-blue crysts (pink in soln) which expl at 225°, The ammonium analogue, [(NHJN,(CO(N,)J, was similar in appearance and props (Ref 1). 

Electron transfer oxidation of 4-methoxyphenol using wjeio-tetraphenylporphyrin as the electron acceptor brings about dehydrodimerization of the phenol to yield 5. The presence of the radical cation of the phenol has been detected by CIDNP techniques. The same product is obtained by irradiation of the tetraphenylporphyrin/benzoquinone/p-methoxyphenol system . Pyrimidinopteridine Af-oxide has been used as a sensitizer to effect the hydroxylation of phenols, also involving the radical cation of the phenol. Thus phenol can be converted to catechol and hydroquinone while cresol yields 4-methyl-catechol . Hydroquinone can itself be oxidized by the cobalt azide complex in aqueous... 

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