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

The coupling of flash vacuum thermolysis reactions (retro [2+2] cleavages) with photoelectron spectroscopy allowed the first direct characterization of several highly reactive N-alkylated silanimines. For the trimethylsilanimine 1b, the IPs corresponding to the ejection of an electron from the nitrogen lone pair (n(N)) and the pi(Si)(=)(N) orbital are observed at 7.9 and 8.3 eV, respectively. In the case of the N-isopropylated and N-tert-butylated analogues 1c,d, these characteristic ionizations are energetically closed (7.8 and 7.4 eV). These unexpected attributions have been corroborated by the ab initiocalculations of the ionization energies using 6-31G(d) and LANL1DZ basis sets and MP2 level. Our results have been completed by the determination of the structural and electronic characteristics of these silanimines.

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