Abstract
Three new nortricyclic P~7~R~3~ derivatives with R = (SiMe~3~)~2~MeSi– (2), (SiMe~3~)~2~PhSi– (3), and cyclo‐Si~6~Me~11~– (4) were synthesized from red phosphorus, sodium/potassium alloy, and a chlorooligosilane, and their structures were elucidated with X‐ray diffraction. Reactions of 2 and 3 and of tri(hypersilyl)heptaphosphane 1 [hypersilyl = (SiMe~3~)~3~Si–] with KO__t__Bu and LiO__t__Bu were performed, which led to different results depending on the size of the substituent. With KO__t__Bu, Si–P bonds were cleaved in 2 and 3, and the mono‐ and dianions [P~7~R~2~]^–^ [R = (SiMe~3~)~2~MeSi: 2a; R = (SiMe~3~)~2~PhSi: 3a] and [P~7~R]^2–^ [R = (SiMe~3~)~2~MeSi: 2b] formed. Crystals of the [K^+.^18‐crown‐6]^+^ salt of 2b suitable for X‐ray diffraction could be grown successfully. Compound 1 reacted in an unprecedented way with KO__t__Bu at –60 °C. An Si–Si bond was cleaved, and a transient silyl anion formed, which immediately rearranged into a transient heptaphosphanide anion [Hyp~2~P~7~]^–^ (1a) under expulsion of bis(trimethylsilyl)silylene. The silylene immediately inserted into a P–P bond of the basal P~3~ ring of 1a, thereby forming two new isomeric anions {Hyp~2~P~7~[Si(SiMe~3~)~2~]}^–^, 1b and 1c. The structure of 1c could be elucidated by X‐ray crystallography, whereas 1b was characterized by ^31^P NMR spectroscopy. The proposed reaction mechanism could be further confirmed by performing the reaction between 1 and KO__t__Bu in the presence of a large excess amount of dimethylbutadiene, which trapped the silylene. Just the formation of anion 1a was observed in that case. Anion 1a was also obtained quantitatively when KO__t__Bu was replaced by LiO__t__Bu. Compound 1a reacted with trifluoroacetic acid to give Hyp~2~P~7~H (1d), which was successfully crystallized and examined by X‐ray diffraction. It is the first structural example of a stable and neutral nortricyclic P~7~ derivative, R~2~P~7~H. All compounds were chracterized further by ^31^P and ^29^Si NMR spectroscopy and elemental analyses.