A series of highly pure tertiary arsines (R3As, where R = Et, Prn, Pri, Bun, Bui, Busec. But, vinyl, allyl, Me3SiCH2, Ph, Bzl, p-tolyl, and mesityl) are conveniently prepared in high yield from the reactions of organo-Al,-Mg,-Li, or-Zn reagents with the chlorodioxarsolane [formula omitted]. We have found that [formula omitted] is a very versatile compound for the synthesis of a wide variety of tertiary arsines. Although similar reactions were carried out using [formula omitted], the yields were poor. This synthetic procedure has been extended to the synthesis of tertiary phosphines. The synthesized arsines were characterized by their IR, NMR, and mass spectra. A complete analysis of the 1H and 13C NMR spectra of each of the arsines was carried out, and the results are discussed in terms of substituent effects and the arsine conformation(s) in solution. © 1990, American Chemical Society. All rights reserved.