Gas-Phase Generation and Photoelectron Spectra of Dimethyl- and Diisopropylsilanethiones¹

Abstract

The flash vacuum thermolysis of propargylthio- and allylthiodialkylsilanes, potential precursors of unhindered silanethiones (R2SiS), has been investigated by photoelectron spectroscopy. This technique allowed us to characterize in the gas phase two very reactive species of this series, dimethyl- and diisopropylsilanethione. According to the values observed for the ionization potentials associated with the ejection of a π electron, the πSi  S double bond is energetically more stable than the earlier studied SiN double bond.

Flash Vacuum Thermolysis Synthesis of New Reactive Compounds Containing a Silicon−Heteroatom Double Bond

“…In conjunction with PES, it has also been characterized directly in the monomeric state. [40] The ionization potentials thus obtained are in agreement with those calculated and observed previously. [36] (Scheme 7).…”

“…[24,35,40] The calculated energies of the two first ionic states, associated with the ejection of an electron from the heteroatom lone pair and from the π SiϭX bond, reflect the experimentally observed ionizations fairly well for all the heterosilenes investigated. This experimental and theoretical data set enables the differences in electronic structure between related SiϭX and CϭX compounds to be specified.…”

Silanones and Silanethiones from the Reactions of Transient Silylenes with Oxiranes and Thiiranes in Solution. The Direct Detection of Diphenylsilanethione.

“…26,48,[51][52][53][54][55][56][57][58] Silanethiones are thought to be more thermodynamically stable than silanones due to a lower polarity of the SidS bond, 26,51,59 and indeed two sterically stabilized, base-free silanethiones have been reported [41][42][43][44] in addition to a few donor-coordinated derivatives. [36][37][38] However, remarkably few transient silanethiones have been observed directly, either in lowtemperature matrixes, 60 the gas phase, [61][62][63] or in solution. 40 In the present paper, we report the results of kinetic and product studies of the reactions of the transient silylenes SiMe 2 and SiPh 2 with cyclohexene oxide (CHO), propylene oxide (PrO), and propylene sulfide (PrS) in hexanes solution.…”

“…Remarkably little quantitative information on the reactivity of these species exists, in spite of considerable interest over the past few decades in the chemistry of silicon-chalcogen double bonds − and the synthesis of stable compounds containing these intrinsically highly reactive moieties. − Several stable silacarbonyl compounds have been reported, − all but one of them containing chelating ligands to stabilize the highly reactive silicon−oxygen double bond. However, a stable dialkyl- or diarylsilanone (with or without chelating ligands) has yet to be reported, and thus, most of our knowledge regarding the spectroscopic properties and structures of these compounds has been gained through low-temperature matrix isolation studies ,,,− and theoretical calculations. ,,− Silanethiones are thought to be more thermodynamically stable than silanones due to a lower polarity of the SiS bond, ,, and indeed two sterically stabilized, base-free silanethiones have been reported − in addition to a few donor-coordinated derivatives. − However, remarkably few transient silanethiones have been observed directly, either in low-temperature matrixes, the gas phase, − or in solution …”

Rotational spectrum and equilibrium structure of silanethione, H2SiS

“…6 Some evidence for diisopropylsilanethione was obtained in flash vacuum thermolysis (FVT) experiments combined with photoelectron spectroscopy. 7 However, up to now, experiments in search for the parent silanethione, H 2 SiQS, failed (e.g. ref.…”