Building und Reaktionen des Phosphanyliden-Phosphorans (tBu)2P?P = PX(tBu)2 (X = Br,Cl) |
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| Authors: | G Fritz B Mayer E Matern |
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| Abstract: | Formation and Reaction of the Phosphanylidene-phosphorane (tBu)2P? P = PX(tBu)2 (X = Br, Cl) The formation of (tBu)2P? P = P(Br)tBu2 1 from (tBu)2P]2PLi and BrH2C? CH2Br begins with an exchange of Li against Br and is then determined by the migration of Br from the secondary P atom in (tBu)2P]2PBr 6 to the primary P in 1 . Similarly, (tBu)2P? P = PC1(tBu)2 2 is obtained starting from PCl3 and LiP(tBu)2. The formation of Phospanylidene—phosporane is not influenced by the choice o the halogene substituent, but the presence of the tBu groups is strongly required. (tBu)2P? P(Li)? P(SiMe3)2 e. g., yields (tBu)2P? P(br)? P(SiMe3)2 with BrH2C? CH2Br; however neither this nor (tBu)2P? P(Cl)? P(SiMe3)2 do rearrange to a Phosphanylidene-phosphorane. The F3C substituent could be neglected in this investigation as (F3C)2P]2P? SiMe3 cannot be lithiated by means of BuLi. Compounds 1 and 2 display a charateristic temperature dependent behavior. While 1 at +20°C decomposes via the reactive intermediate (tBu)2P? P to from the cyclophosphanes P3P(tBu)2]4, it gives crystals of (tBu)2P]2P? pP(tBu)2]2 at ?20°C (from a solution in toluene). Reacting 1 with tBuLi produces (tBu)2P? P = P(H)tBu2 20 and (tBu)2P? P(H)? P(tBu)2 14 . Initially, a transmetallation yield tBuBr and (tBu)2 P? P=Pli(tBu)2 21 ,then LiBr and isobutene are eliminated and 20 is formed which can rearrange to produce 14 . Without the elimination of isobutene, 1 react with nBuLi to give 21 witch can be trapped with Me3SiCl as (tBu)2P? P(tBu)2 23 . The main product in in this reaction is however (tBu)2P]2P? nBu 22 . |
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| Keywords: | Reaction of (tBu)2P?P=PX(tBu)2 (X = Br Cl) |
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