Taming a silyldiium cation and its reactivity towards sodium phosphaethynolate.

A dicationic bis(NHC)-stabilised silyldiium complex, [bis(NHC)-SiPh] (7) (bis(NHC) = [CH(NCHNDipp)], Dipp = 2,6-PrCH), was synthesised for the first time. It reacts with sodium phosphaethynolate (NaOCP) as a source of monoanionic phosphorus to give the P-insertion product [bis(NHC)-PSiPh] (8). The latter comprises a seven-membered heterocycle containing a Si-P moiety which can easily be desilylated when exposed to dichlorophosphanes as exemplified by the synthesis of the diphosphanide cations [bis(NHC)-PPCy] (9) and [bis(NHC)-PPPh] (10).