Taming a silyldiium cation and its reactivity towards sodium phosphaethynolate.

A dicationic bis(NHC)-stabilised silyldiium complex, [bis(NHC)-SiPh2]2+ (72+) (bis(NHC) = [CH2(NC3H2NDipp)2], Dipp = 2,6-iPr2C6H3), 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)-PSiPh2]+ (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+).