First gas-phase generation of a cis chloroiminoarsane ClAs NSiMe and a cis chloroiminophosphane ClP NSiMe Bu. Characterization by photoelectron spectroscopy
Résumé
Photoelectron spectroscopy-flash vacuum thermolysis in the gas phase allowed us to synthesize, for the first time, the cis forms of two weakly hindered, low-coordinate arsenic and phosphorus compounds (ClPn NSiR3; Pn = P, As), as well as to characterize them by their ionization energies. In order to assign the different bands in the PE spectra and to estimate the effect of the substituents SiMe3 and Cl on the electronic and structural properties of these compounds, we performed calculations using density functional theory (hybrid functional B3LYP) with the basis set 6-311G(d,p). The thermodynamic stabilization of these halogenated systems appears in the important antiperiplanar interactions between the nitrogen lone pair nNand the σ*AsCl (or σ*PCl) orbital. For these two compounds, in spite of a poor 2pπ(N)-3pπ(P)/4pπ(As) overlap, it was observed that the substitution of a chlorine atom on the pnictogen (As,P) and a silyl group on nitrogen (negative hyperconjugation) leads to a relatively high ionization energy for the πPn N orbital [IE(πPn N ≈ 10 eV].