Reaction Products of Methylene Iodide with Tertiary Arsines

Abstract

The reactions products of tertiary arsines with methylene iodide are (iodomethyl)trialkyl(aryl)-arsonium iodides. Treatment of the latter with lead(II) nitrate in aqueous ethanol solutions gives rise to an exchange reaction to form the corresponding nitrates in high yields.Tertiary arsines, both symmetrical and mixedradical, react with organyl halides to give tertiary arsonium salts [1]. The fourth bond is formed by coordination of antibonding 4s 2 electrons of trivalent arsenic with trivalent Lewis acids. As a result, cationic complexes are formed [2]. Nucleophilic properties of trialkyl(aryl)arsines depend not only on the existence of the above-mentioned electron pair, but also on the character of substituents on the central atom, and, what is most important, on the composition and structure of the electrophilic reagent, that is organyl halide [3].Michaelis [4] has been the first to show that triphenylarsine is alkylated with diiodomethane at 130oC to form an adduct with the following proposed composition and structure.(C 6 H 5 ) 3 As E A CH 2 I I From this structure it follows that the arsenic atom in it, as well as in all other five-coordinate arsenic compounds should be sp 3 d-hybridized, and the geometry of the product should be trigonal bipyramid [5]. No more recent data on the alkylation with methylene iodide of other trialkyl(aryl)arsines are available.To gain more information on the ability of diiodomethane to exhibit electrophilic properties in reaction with tertiary arsines of various compositions and structures, as well as to assess the structure of the reaction products, in the present work we performed a more thorough study of the reaction of trialkyl(aryl)-arsines with methylene iodide.It was found that methylene iodide reacts with tertiary arsines, including those with mixed radicals, to form tertiary arsonium iodides IIa3IIh [reactions (1) and (2)].