Arsenic III bromide

Submitted by FRANCISCO J. ARNAIZ and MARIANO J. MIRANDA Checked by ARNOLD L. RHEINGOLD  

This reaction allows for the preparation of 50-60 g of pure AsBra in less than 2 h and can be scaled without difficulty. 

In a 250-mL Erlenmeyer flask are placed 20 g (0.051 mol) of AS4O6 powder, 160 mL of 48% HBr, and a magnetic stirring bar. The mixture is heated with stirring at 120°C for 10-20 min until all the arsenic oxide is dissolved. The mixture is cooled in an ice bath and a significant amount of white solid separates. The aqueous solution is decanted, and the solid is treated with 100 mL of hexane at room temperature (in case two phases are produced, the minor aqueous phase 

AsBra is a colorless crystalline solid that melts at 32°C and hydrolyzes slowly in air developing a white color. It is very soluble in common aprotic solvents, including hydrocarbons and ethers. The IR spectrum, KBr dispersion, has characteristic j/AsBr bands at 272 and 287 cm .  

Doak and L. D. Freedman, in Organometallic Compounds of Arsenic, Antimony and Bismuth, Wiley-Interscience, New York, 1970. 

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Arsenic tribromide (arsenic(III) bromide), AsBr, is similar to the trichloride. The dielectric constant at 35°C is 8.33. The compound is usually made by treating arsenic with a solution of bromine in carbon disulfide. 

The use of organotin compounds for the preparation of organometallics and organometalloids appears to be quite versatile.9 For example, alkyltetrafluorophosphoranes have been obtained from tetraalkyltin compounds and phosphorus(Y) fluoride,10 phenylmercury(II) chloride from tetraphenyltin and mercury(II) chloride,11 and divinylbromoarsine from ( -C4H9)2-Sn(CH=CH2)2 and arsenic (III) bromide.12... 

Pure arsenic(iii) bromide could be prepared by the treatment of AS4O6 152 with HBr in high yield (81%). However, the yield is reduced if the evacuation is prolonged after removal of the extraction solvent (hexane), since the vapor pressure of AsBrs is significant, although AsBts is a colorless crystalline solid that melts at 32 °C (Scheme 50) <2002IS(33)203>. 

Just as certain chlorides are found to behave as useful solvents for the formation of chloro-complexes, bromo-complexes are formed in solutions of the corresponding bromides. The solvent behaviour of (for example) molten iodine mono-bromidei53 molten arsenic(III) bromide 54-156 aluminium (III) bromidei " or molten mercury(II) bromide -i has been described the chemistry in such solutions has been briefly re vie wed s 123,124 Hydrogen bromide is very similar, but has been discussed separately in this presentation as a protonic acceptor solvent (chapter IV). 

Iodine bromide and arsenic(III) bromide resemble closely as solvents iodine monochloride and arsenic(III) chloride respectively, and stable acids have not been isolated in the bromo-systems. Molten mercury(II) bromide is an excellent solvent for various classes of compounds. Alkali metal bromides form solvated anionic species which appear to contain the ions [IBr2] , [AsBr4] and [HgBr3] respectively and phosphorus(V) bromide gives PBr4+IBr2 in iodine bromide where it behaves as a base. Other basic substances are nitrogenous bases such as pyridine. 

All soluble bromides of the alkali metals and alkaline earth metals behave as solvo-bases in the respective covalent bromide solvent systems under consideration. While in iodine bromide and in aluminium bromide only few and very weak solvo-acids have been found, various acceptor bromides react readily with bromides in solutions of arsenic(III) bromide and mercury(II) bromide. 

Iodine bromide converts various metals into the bromides its reactivity is smaller than that of iodine monochloride. Arsenic(III) bromide reacts with the oxides of lead, gold or copper to give the respective bromides ... 

AsBr, Arsenic(III) bromide 31.1 11.7 BrRb Rubidium bromide 682 15.5... 

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