Abstract

A series of aryl-arsonium and -stibonium salts bearing an imino substituent in the ortho position to the cationic centre has been prepared by the reactions of ortho-halogenoarylimines with triaryl-arsines and -stibines in the presence of copper(I) iodide in acetonitrile. X-Ray crystal structural studies reveal the existence of intramolecular coordination from the imino nitrogen to arsenic and antimony, with consequent distortion of bond angles about the group 15 element, which adopts a trigonal bipyramidal structure. Deprotonation of arsonium and stibonium salts derived from ortho-halogenoaryliminophenols gives a series of highly coloured aryl-arsonium and -stibonium iminophenolate betaines, which have been shown to exhibit a significant degree of negative solvatochromism, similarly to their previously reported arylphosphonium analogues. The visible absorption properties and solvatochromism are largely independent of the nature of the group 15 element, implying little d-orbital contribution to bonding in either ground or excited states.