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Dedicated to Professor Herbert Griinewald on the occasion of his 60th birthdayJust as the octet rule had prevented the discovery of the inert-gas compounds, the systematic search for phosphorus-carbon-and phosphorus-nitrogen-compounds having (p-p)nmultiple bonds was hindered by the double bond rule. The first successful synthesis of mesomeric-stabilized phosphorus-carbon compounds with coordination number 2, seventeen years ago, was followed nine years later by the preparation of the imino-phosphanes whose intensive investigation has continued to the present day. A dramatic development has now begun in the phospha-alkene and -alkyne fields, and a large variety of preparative methods have been found. Several compounds of this type are amazingly stable, however they do not participate in typical ylide reactions such as the Wittig reaction. In contrast, the PC double bond is more comparable to that of olefins, which has been confirmed by the occurrence of E,Z-isomers and pericyclic reactions of phospha-1,s-hexadienes.

Die Synthese neuartiger, silylierter Bisiminophosphorane des Typs Ph2P(NSi(CH3)3)(CH2)(n)PPh2(NSi(CH3)3) 2a, b und c mit n = 1, 2, 3 und des analog gebauten cyclischen Silins 5 erfolgt durch Umsetzung der betreffenden Alkylenbisphosphine mit Silylaziden. Die offenkettigen Vertreter 2a und b werden von ätherischer HCl desilyliert; sie kondensieren – ebenso wie 5 – mit den Fluorphosphoranen PhxPF5–x(x = 0, 1) unter Fluorsilanabspaltung zu den ionischen, partiell fluorierten Diphosphazaphosphonium‐Ringsystemen 7a, b und 8. Die Identifizierung und Charakterisierung der Reaktionsprodukte erfolgt vor allem durch 19F‐ und 31P‐NMR‐Spektroskopie.

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