Unlocking Some Si‐Centered Reactivity of a 4,4’‐Dichloro‐1,4‐di‐hydro‐1,4‐phosphasiline

Abstract To establish some steric protection at the P center of a tricyclic 1,4‐dihydro‐1,4‐phosphasiline, the potassium salt of a tricyclic 1,4‐dihydro‐1,4‐phosphasilin‐1‐ide was treated with triphenylmethyl chloride. Subsequently, the two Si‐bound diethylamino groups, were converted to give the SiCl 2 derivative using HCl. The Si‐functionality could be used in substitution reactions thus giving Si‐dimethyl and Si‐dimethoxy derivatives. Reduction of the SiCl 2 derivative at low temperature gave transient tricyclic silylene which could not be detected by NMR spectroscopy but successfully trapped by 1,3‐butadiene to give a P‐containing spiro‐silolene derivative. DFT studies provide insight into reduction and the silylene formation.