Antimony Compounds

Abstract

Antimony is the fourth member of the nitrogen family and has a valence shell configuration of 5 s 2 5 p 3 . The utilization of these orbitals and, in some cases, of one or two 5 d orbitals permits the existence of compounds in which the antimony atom forms three, four, five, or six covalent bonds. A recommended exposure limit for antimony compounds of 0.5 mg/m 3 (as Sb) has been given. Disposal may be effected by washing residues down the drain at very high dilution unless prohibited by local regulations. Stibine, SbH 3 , is a colorless, poisonous gas having a disagreeable odor. It is the only well‐characterized binary compound of antimony and hydrogen. Stibine is readily oxidized and may be ignited in the presence of air or oxygen to form water and antimony trioxide; at lower temperatures metallic antimony and water are slowly formed. High purity stibine is used as an n ‐type, gas‐phase dopant for Si in semiconductors. The most important binary compounds of antimony with metallic elements are indium antimonide, InSb, gallium antimonide, GaSb, and aluminum antimonide, AlSb, which find extensive use as semiconductors. Antimony trioxide is insoluble in organic solvents and only very slightly soluble in water. Antimony trioxide has numerous practical applications. Its principal use is as a flame retardant in textiles and plastics. Antimony tetroxide finds use as an oxidation catalyst, particularly for the dehydrogenation of olefins. Antimonic acid has been used as an ion‐exchange material for a number of cations in acidic solution. Antimony trifluoride is used as a fluorinating agent to replace nonmetal chloride with fluorine. Antimony trichloride is used as a catalyst or as a component of catalysts to effect polymerization of hydrocarbons and to chlorinate olefins. It is also used in hydrocracking of coal and heavy hydrocarbons. Both antimony tribromide and antimony triiodide readily hydrolyze, form complex halide ions, and form a wide variety of adducts with ethers, aldehydes, mercaptans, etc. Antimony pentafluoride is a strong Lewis acid and a good oxidizing and fluorinating agent. Antimony pentachloride is a strong Lewis acid and a useful chlorine carrier. Antimony trisulfide is used in fireworks, in certain types of matches, as a pigment, and in the manufacture of ruby glass. Antimony pentasulfide, Sb 2 S 5 , commercially known as golden sulfide of antimony, is used in vulcanization to produce a red variety of rubber. The material is also used as a pigment and in fireworks. A large number of compounds have been prepared in which the antimony atom is linked to carbon through an oxygen or sulfur atom. By far the largest group are those obtained by reaction of an antimony oxide with an α‐hydroxy acid, o ‐dihydric phenol, sugar alcohol, or some other polyhydroxy compound containing at least two adjacent hydroxyl groups. The best known compound of this type is antimony potassium tartrate (tartar emetic), used as an antiparasitic agent in medicine. A wide variety of compounds containing the Sb–C bond is known. Organoantimony compounds can be broadly divided in Sb(III) and Sb(V) compounds. A large number of trialkyl‐ and triarylstibines are known. Tertiary stibines have been widely employed as ligands in a variety of transition‐metal complexes, and they appear to have numerous uses in synthetic organic chemistry, eg, for the olefination of carbonyl compounds. They have also been used for the formation of semiconductors, as catalysts or cocatalysts for a number of polymerization reactions, as ingredients of light‐sensitive substances, and for many other industrial purposes. A considerable number of tetraalkyl‐ and tetraaryldistibines have been investigated. A number of organoantimony compounds containing rings of four, five, or six antimony atoms have been prepared. Antimonin(stibabenzene), C 5 H 5 Sb, the antimony analogue of pyridine, can be prepared by the dehydrohalogenation of a cyclic chlorostibine. The stibonic and stibinic acids are polymeric compounds of unknown structure. Dialkylstibinic acids can be readily prepared. Both aliphatic and 'aromatic stibine oxides, R 3 SbO, or their hydrates, R 3 Sb(OH) 2 , are known, as are both trialkyl‐ and triarylstibine sulfides and selenides. Both dialkyl‐ and diaryltrihaloantimony compounds are known. The best known of the halides are the trialkyldihalo‐ and triaryldihaloantimony compounds. Dichlorotriphenylantimony has been suggested as a flame retardant and as a catalyst for the polymerization of ethylene carbonate. Dibromotriphenylantimony has been used as a catalyst for the reaction between carbon dioxide and epoxides to form cyclic carbonates and for the oxidation of α‐keto alcohols to diketones. In addition to the trialkyldihalo‐ and triaryldihaloantimony compounds, mixed dihalo compounds such as chloroiodotriphenylantimony, (C 6 H 5 ) 3 SbClI, have been reported. Tetraalkyl and tetraaryl compounds, R 4 SbX, are well‐known and are often referred to as stibonium salts. There is evidence, however, that most of the tetraaryl compounds contain pentacovalent antimony. In contrast to phosphorus and arsenic, only a few antimony ylids have been prepared. A new method, utilizing an organic copper compound as a catalyst, has resulted in the synthesis of a number of new antimony ylids. A number of pentaalkyl‐ and pentaalkenylantimony compounds have been prepared from tetraalkyl‐ or tetraalkenylstibonium halides and alkyl or alkenyllithium or Grignard reagents. Compounds of antimony have been used as therapeutic agents for thousands of years. The toxicity of these substances was noted at an early date. The therapeutic use of antimonials reached a peak during the eighteenth or early nineteenth century. The introduction of antimony compounds for the treatment of parasitic diseases (eg, American mucocutaneous leishmaniasis, visceral leishmaniasis, and oriental sore) is undoubtedly one of the important milestones in the history of therapeutics. Therapeutic compounds include antimony potassium tartrate (tartar emetic), antimony(V) sodium gluconate, and meglumine antimonate.