Ethynylarsine (2a) is synthesized by reaction of arsenic trichloride with ethynyltributylstannane followed by a chemoselective reduction of the formed ethynyldichloroarsine (la). The base-induced rearrangement of compound 2a on a solid base in VGSR conditions leads to ethylidynearsine (3a) characterized by 1 H and 13C NMR and by microwave spectroscopy. The rotational spectrum of 3a is recorded in the frequency range 90-470 GHz. Rotational and centrifugal distortion constants are determined and the quadrupole hyperfine structure is analyzed. The structure of CH~CIAS has been estimated from the rotational constants of eight different isotopic species and from ab initio calculations. Compound 3a exhibits a low stability at 0 OC in deuteriochloroform (~1 1 2 ca. 1 h) or in the gaseous phase at a pressure of 10 Pa (~1 / 2 ca. 30 min).

International audiencePrimary unsaturated stibines ethenylstibine (la), E-prop-1-enylstibine (1b), ethynylstibine (2a), and prop-1- ynylstibine (2b) are synthesized by reaction of antimony trichloride with the corresponding vinyltributylstannanes 3a,b and alkynyltributylstannanes 4a,b, respectively, followed by a chemoselective reduction of the formed dichlorostibines Sa,b and 6a,b. Compounds la,b and 2a,b are characterized on the basis of spectral data (NMR, photoelectron spectroscopy and high resolution mass spectrometry). In particular, the PE spectra display very well-resolved bands (1a, 9.3, 10.3, 11.2, 11.9, 13.7, and 15.0 eV; 2a, 9.7, 10.5, and 11.2 eV). The α-unsaturated stibines exhibit a low stability at room temperature even in the presence of a solvent (τ1/2 ca. 1 h) and lead to the formation of oligomeric material or an antimony mirror on the wall of the flask. Attempts to detect C-Sb multiple bond derivatives by a base-catalyzed rearrangement of 1 or 2 were unsuccessful. © 1995, American Chemical Society. All rights reserved

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