Gas-phase generation and photoelectron spectra of dimethyl- and diisopropylsilanethiones

The flash vacuum thermolysis of propargylthio- and allylthiodialkylsilanes, potential precursors of unhindered silanethiones (R2Si=S), has been invest igated by photoelectron spectroscopy. This technique allowed us to characte rize in the gas phase two very reactive species of this series, dimethyl- a nd diisopropylsilanetkione. According to the values observed for the ioniza tion potentials associated with the ejection of a pi electron, the pi(Si=S) double bond is energetically more stable than the earlier studied Si=N dou ble bond.