Über Arsen-haltige Heterocyclen. II. Molekül- und Kristallstruktur von 5-Chlor-1-oxa-4,6-dithia-5-arsaocan

On Heterocyclic Systems Containing Arsenic. II¹). Molecular and Crystal Structure of 5-Chloro-1-oxa-4, 6-dithia-5-arsaocane The crystal structure of the title compound has been determined from single crystal X-ray data and refined to a conventional R of 0.048. The eight-membered ring has the boat-chair conformation. PITZER and BAEYER strain are smaller than in cyclooctane and the transannular 1, 5-H…?H repulsion in cyclooctane is replaced by a stabilizing 1, 5-As…?O attraction. The coordination of the As-atom is ψ trigonal-bipyramidal with axial distances As? Cl 2.27 Å, As? O 2.45 Å and equatorial distances As? S 2.25 Å. The structure consists of 12-coordinated molecules. The crystal data of the analogous Sb compound 5-Chloro-1-oxa-4, 6-dithia-5-stibaocane are given.