Acyl- und Alkylidenphosphane. XXVI. 2, 4-Bis(phenylimino)-1,3-diphosphetane aus Thiocarbamoyl- und Carbamoyltrimethylsilylphosphanen

Acyl-and Alkylidenephosphines. XXVI. 2, 4-Bis (phenylimino)-1, 3-diphosphetanes from Thiocarbamoyl- and Carbamoyltrimethylsilylphosphines . Bis(trimethylsilyl)phosphines R? P? Si(CH₃)₃]₂ 1 (R = H₃C a, H₅C₆ b, (H₃C)₃C e, H₁₁C₉ d) and phenyl isothiocyanate give insertion compounds which were identified as CN-phenyl, N-trimethylsilyl)thiocarbamoyl]trimethylsilylphosphines 3 ? 2 in solution as well as in the solid state 2]. In the presence of small amounts of solid sodium hydroxide the phenyl derivative 3 ? 2b eliminates bis(trimethylsilyl) sulfane, whereas the tert-butyl 3 ? 2c and the mesityl compound 3 ? 2d show the same reaction even without a catalyst. The unstable (phenylimino)methylidene]phosphines 6 formed first, dimerize rapidly to give 2, 4-bis(phenylimino)-1,3-diphosphetanes 7 which in solution exist as mixtures of the E and Z isomers. Via a NaOH-catalyzed elimination of hexamethyldisiloxane these cyclic phosphines 7 can also be obtained from the adducts of phenyl isocyanate and bis(trimethylsilyl)phosphines 1. Taking the thermally sufficiently stable tert-butyl derivative 7 c as an example, the temperature dependence of n.m.r. spectra is discussed in detail.