Die Phosphide LiR2P7, Li2RP7 (R = Me3Si,Et, iPr,iBu) und alkyliert-silylierte Heptaphosphane(3)

The Phosphides LiR₂P₇, Li₂RP₇ (R = Me₃Si, Et, iPr, iBu) as well as Mixed Alkylated and Silylated Heptaphosphanes(3) Formation and properties of LiR₂P₇ and Li₂PR₇ (R = Me₃Si, Et, iPr, iBu) and their reactions with Me₃SiCl or alkylhalides yielding mixed alkylated and silylated heptaphosphanes(3) are reported. Reactions of (Me₃Si)₃P₇ and Li₃P₇. 3 DME produce mixtures of Li(Me₃Si)₃P₇, Li₂(Me₃Si)P₇ and Li₃P₇ from which pure Li(Me₃Si)₂P₇ (s, as) can be isolated by means of an extraction with toluene. Similarly, the isomers of LiR₂P₇ (R = Et, iPr, iBu) can be extracted from the mixtures obtained by reacting Li₃P₇ with alkylbromides. The (s) isomers of LiR₂P₇ in solution at about 20°C from the (as) isomers whereas the latter up to 70°C do not show any inversion. The (as) lithiumdialkylphosphides can be obtained as ether free products (red brown powder, isoluble in toluene, soluble in THF) by repeated addition of toluene and removal of the solvents; the (s) isomers decompose during the procure. In reactions of LiEt₂P₇. THF (s, as) in toluene at ?30°C with EtBr only the (s) isomer is substituted and gives Et₃P₇ (s), however on warming to 20°C by inversion of P^e a ratio of (s) : (as( = 1 : 3 is obtained. With Li(iBu)₂P₇, (s) reaction begins above ?20°C the giving both the (s) and the (as) isomer. (iBu)₃P₇ (s) is the prefered isomer at higher temperatures. Li(Me₃Si)₂P₇ (s, as) with Me₃SiCl exclusively yields (Me₃Si)₃P₇ (s). Li₂RP₇ (R = alkyl, Me₃SI) is not available. From mixtures with LiR₂P₇ and Li₃P₇, it can be isolated only after repeated cumbersome extraction of LiR₂P₇ as was shown with Li₂(iPr)P₇ as an example. Ether free LiEt₂P₇(s, as) with Me₃SiCl exclusively gives Et₂(Me₃Si)P₇ (s, as) whereas LiEt₂P₇ ? THF due to its THF content does not. Similarly, ether free Li(iBu)₂P₇ yields (iBu)₂(Me₃Si)P₇ (s, as). The compounds R(Me₃Si)₂P₇ (R = alkyl) cannot be selectively prepared neither starting from Li₂RP₇ with Me₃SiCI) nor from Li(Me₃Si)₂P₇ with RX. Such, the reaction of Li(Me₃Si)₂P₇ ? THF with EtBr in toluene at ?78°C yield a mixture of Et(Me₃Si)₂P₇ (42%), Et₂(Me₃Si)P₇ (27010), (Me₃Si)₃P₇ (29%) and Et₃P₇ (2%). (Me₃Si)₃P₇ with MeI in a molar ratio of 1 : 1 at 70°C quantitatively produces Me(Me₃Si)₂P₇ whereas already using a molar ratio of 1 : 2 also Me₃P₇ is obtained. With EtBr mixtures of Et(Me₃Si)₂P₇ and Et₃P₇ are formed. iBuBr gives iBu₃P₇, but tBuBr does not yield any tBu₃P₇.