Chemie polyfunktioneller Moleküle. 93. Die halogenierende Ringspaltung des As₃-Nortricyclans, 4-Methyl-1,2,6-triarsatricyclo[2.2.1.0^2,6]heptan Darstellung und Eigenschaften von 2,6-Dihalogen-4-methyl-1,2,6-triarsabicyclo[2.2.1]heptanen^†

Chemistry of Polyfunctional Molecules. 93. Halogenating Ring Cleavage of As₃-Nortricyclane 4-Methyl-1,2,6-triarsatricyclo[2.2.1.0^2,6]heptane. Preparation and Properties of 2,6-Dihalogeno-4-methyl-1,2,6-triarsabicyclo[2.2.1]heptanes

The reaction of the As₃-nortricyclane CH₃C(CH₂As)₃ (1) with PCl₅, Br₂, or I₂ in a molar ratio of 1:1 leads to the new 2,6-dihalogeno-4-methyl-1,2,6-triarsabicyclo[2.2.1]heptanes CH₃C(CH₂As)₃X₂ (X = Cl, Br, I; 2a–c). Application of a molar ratio of 1:2 results in the formation of 1,1,1-tris(dihalogenoarsinomethyl)ethanes CH₃C(CH₂AsX₂)₃ (4a–c) in rather poor yields; ¹H-NMR spectroscopic studies suggest that 4a–c are formed via 2a–c and the tetrahalogenodiarsacyclopentane derivatives (3a–c); the latter can not be isolated from their solutions. 4a–c are obtained in very good yields by treatment of 1 with the halogenating agents in a molar ratio of 1:3 Comproportionation of 1 with 4a–c (molar ratio of 2:1) gives also 2a–c. Whereas in CD₂Cl₂ or CS₂ disproportionation of 2a leads to an equilibrium between 1 and 4a, which is formed via the intermediate 3a. The homologues 2b, c are stable with respect to disproportionation in both solvents.