Synthesis, Characterisation and Properties of As-Monohalogenated Dibenzoarsocines S(C6H4S)2AsHal (Hal = Cl, Br, I) A Study of the Transannular Interaction S?As

Addition of AsCl3 to S(C6H4SH)2 in benzene solution leads to the formation of the stable compound S(C6H4S)2AsCl (1). The S(C6H4S)2AsHal [Hal = Br (2), I (3)] compounds have been synthesised by halogen exchange from 1 and the corresponding potassium halide. X-ray structure determinations of complexes 13 reveal that the arsenic atom acts as an acceptor atom exhibiting an intramolecular transannular interaction with the thioether-like sulfur atom. The geometry of the tetracoordinate As atom in the title compounds is described as distorted pseudo-trigonal-bipyramidal with a stereochemically active lone pair and 6663?% trigonal-bipyramidal character. The transannular interaction influences the conformation of the dibenzotrithiarsocine system, adopting the central eight-membered ring with a boatboat conformation and Cs symmetry.