Antimony pentachloride solubility

Evidence that the reaction of the diol ester 5 with antimony pen-tachloride genuinely involves a neighboring-group reaction is provided by the stereospecificity of this reaction with esters of cyclic diols. trans -l,2-Cyclopentanediol diacetate (14) and Irons-1,2-cyclo-hexanediol diacetate (17) react " with antimony pentachloride to give the cis-acetoxonium salts 15 and 18, whereas the cis-diol esters (16 and 19) merely give difficultly soluble adducts from which unchanged starting material can be recovered after hydrolytic treatment. 

On treatment in carbon tetrachloride with antimony pentachloride, tri-0-acetyl-/3-D-xylopyranosyl chloride (69), tetra-0-acetyl-/3-D-xylo-pyranose (70), and tri-O-acetyl-a-D-xylopyranosyl chloride (71) give an acetoxonium salt that precipitates directly from the solution. This salt consists of a mixture of the D-xylo, B-lyxo, and D-arabino derivatives (72, 73, and 74, respectively). None of these three compounds crystallize out preferentially. Evidently, the D-xylo derivative 72 is formed initially, and is then transformed by reversible acyloxonium rearrangements into 73 and 74. Salts are not isolated when the reaction is conducted in dichloromethane, because of their high solubility in this solvent. 

Most soluble antimony compounds are colorless crystals or powder the pentachloride is a colorless to yellow fuming liquid with an offensive smell.1... 

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