Reaktive E=C(p-p)π-Systeme, XXVIII / Reactive E=C(p-p)π-Systems, XXVIII : Synthese und Reaktivität des Iminomethylenphosphans F3C-P=C=N-tBu / Synthesis and Reactivity of the Iminomethylenephosphane F3C-P=C=N-tBu

The reaction of perfluoro-2-phosphapropene F₃CP=CF₂ (1) with tert-butylamine or isopropylamine in a 1:3 molar ratio leads to the novel iminomethylene phosphanes F₃CP=C=N(tBu) [(2), 30% yield] and F₃CP=C=N(iPr) [(3), 5%], respectively. 2 slowly decomposes at room temperature giving tert-butylisonitrile and the cyclophosphanes (F₃CP)ₙ (n = 3, 4, 5). 3 is found to be less stable than 2 and for example is attacked by primary amines. The reaction of 2 with 2,3-dimethyl-1,3-butadiene or trimethylphosphane yields, on the one hand, the cycloaddition product of bis(trifluormethyl)diphosphene (4), and on the other hand, the phosphorus ylid Me₃P=PCF₃ (5) together with (tBu)NC.2 and 3, respectively, are not obtained from (F₃C)₂PH and the corresponding primary amines in a series of HF elimination and H₂NR addition reactions. The main products formed from a 1:4 molar mixture of (F₃C)₂PH and H₂N(iPr) in a one-pot procedure were shown to be the chiral phosphanes F₃CP[NH(iPr)]C[=N(iPr)]H (6), F₃CP[NH(iPr)]CHF₂ (7) and F₃CP[NH(iPr)]CH₂F (8) (60:35:5). The corresponding reaction of (F₃C)₂PH with H₂N(tBu) mainly yields the compound F₃CP[NH(tBu)]CH₂F (10).