Stibinic acid

Stibonic and Stibinic Acids. The stibonic acids, RSbO(OH)2, and stibinic acids, R2SbO(OH), are quite different in stmcture from their phosphoms and arsenic analogues. The stibonic and stibinic acids are polymeric compounds of unknown stmcture and are very weak acids. lUPAC classifies them as oxide hydroxides rather than as acids. Thus CgH3SbO(OH)2 is named phenyl antimony dihydroxide oxide [535-46-6], the Chemical Abstracts n.2ixn.e is dihydroxyphenylstibine oxide [535-46-6], CgH OgSb. 

Dimethyl stibinic acid [35952-95-5], C2H202Sb, diethylstibinic acid [35952-96-6], C4H 02Sb, dipropylstibinic acid [35952-97-7], CgH 302Sb, and dibutylstibinic acid [35952-98-8], CgH2202Sb, have been prepared in this manner. Except for the dimethyl compound, they can be readily recrystaUi2ed from organic solvents. 

Bis-(p-nitrophenyl)antimony trichloride 526 Iron powder (2 g, 0.036 mole) is added at 0°, during 35-40 min, with vigorous stirring, to a solution of p-nitrobenzenediazonium chloride-1-antimony trichloride (15 g, 0.036 mole) in anhydrous acetone (45 ml), and the whole is then stirred for a further 40 min. The inorganic solid is removed and the filtrate is evaporated. The residual product is treated with 5N-hydrochloric acid (50 ml) and then with 96% ethanol (25-30 ml). The resulting mixture is poured into 5 % ammonia solution (excess) containing ice this precipitates bis-(p-nitrophenyl)stibinic acid (7 g, 97%), which is then converted into the trichloride by crystallization from 5N-hydrochloric acid. 

All the dihalides are solids, the melting-points rising as the number and weight of the substituents in the benzene nucleus increases. Treatment of their alcohohc solutions with sodium sulphide or hydrogen sulphide converts them to sulphides. Chlorine readily adds on to yield tetrahalides, which are transformed by moisture to stibinic acids. m-Aminophenyldichlorostibine hydrochloride is slowly decomposed in aqueous solution yielding antimony trioxide and m-diaminodiphenyi-chlorostibine. 

According to this representation a diazostibinic acid is produced, simple evolution of mtrogen then giving the stibinic acid. Such a... 

The arylstibmic acids also possess the properties of colloids, similar to the case of the tri- and tetra-hydi ates of antimony pentoxide. An alkaline solution of a stibinic acid, when titrated with a mineral acid, soon becomes turbid, and when sufficient acid has been added to neutralise the whole of the alkali present, the turbidity becomes more marked. According to Schmidt the turbid solutions possess the properties of hydrosols, and an excess of acid is required to precipitate the colloidal acids from the turbid solutions. 

The formation f complexes takes place with all primary aryl-stibinic acids, the substituents in the ring exerting an effect on the nature of the final product,... 

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