PHOSPHINOMETHANIDES AND GROUP-15 ELEMENT HALIDES - REDOX REACTIONS, REARRANGEMENTS AND NOVEL HETEROCYCLES

The reactions of ECl3 (E = P, As, Sb, Pi), RPCl2 (R = Me, Ph, Bu-t, Cy 2N) and Ph2PCl, respectively, with ambident lithium phosphinomethanide s are described. The reaction with LiCH2PMe2, 1, by E-C bond formation , leads to the substitution products E(CH2PMe2)(3), 2a-d, (E = P, As, Sb, Bi) and R-P(CH2PMe2)(2) (R = Me, Ph, Bu-t, Cy2N) 5a-d. In contrast , LiC(PMe2)(SiMe3)(2). 0.5TMEDA, 6, gives substitution products with E Cl3 (E = P, As, Sb), by E-P bond formation. Thus, the first element-tr is(P-ylide)derivatives E(PMe2=C(SiMe3)(2))(3), 7a-c, are obtained. 7b is characterized by X-ray structure determination. In these reactions, oxidative P-P coupling to give [(Me3Si)(2)C=PMe2](2), 8, is also obse rved, and exclusively in the reaction of BiCl3 with 6. The reaction of RPCl2 (R = Me, Ph, Bu-t, Cy2N) with 6 strongly is dependent on the na ture of R. For R = Me, only substitution is observed, yielding Me-P(PM e2=C(SiMe3)(2))(2), 10, while for R = Ph, both substitution and Li/Cl exchange with subsequent formation of 8 and the diphosphane [(Me3Si)(2 )C=PMe2-PPh](2), 12, are found. The latter has been characterized stru cturally. In contrast, for R = Bu-t, only ((BuP)-Bu-t)(3), 13, and ((B uP)-Bu-t)(4), 14, are obtained. An analogous result is observed in the reaction of (BuPCl2)-Bu-t with LiC(PMe2)(2)(SiMe3), 17. The reaction of Cy2NPCl2 with two equivalents of LiC(PMe2)(SiMe3)(2).0.5TMEDA, 6, g ives a phospha-alkene Cy2N-P=C(SiMe3)(2), 16, and the substitution pro duct Cy2N-P(PMe2=C(SiMe3)(2))(2), 15. Likewise, LiC(PMe2)(2)(SiMe3), 1 7, reacts with PhPCl2 to give the substitution product Ph-P(PMe2=C(PMe 2)(SiMe3))(2), 18, which is characterized by X-ray structure determina tion, whereas with MePCl2 only the P-ylide Me2P-PMe2=C(PMe2)(SiMe3), 2 0, and the coupling product [(Me2P)(Me3Si)C=PMe2](2), 19, are formed. The latter is also obtained in the reactions of BiCl3 or SbCl3 with Li C(PMe2)(2)(SiMe3), 17. Analogous redox reactions with AsCl3 and PCl3, respectively, lead to the bis-pentacyclic {mu-[C(PMe2)(2)(SiMe3)]As-2} (2), 21, and the hexacycle P-PMe2-C(SiMe3)-PMe2-C(SiMe3)-PMe2, 22, whi ch were structurally characterized by X-ray analyses. Depending on the reaction conditions, the reaction of PCl3 with LiC(PMe2)(2)(SiMe3), 1 7, alternatively may lead to the triphosphete P-PMe2-C(SiMe3)-PMe2, 24 . By using P-phenyl-substituents instead of P-methyl-substituents, i.e . in the reaction of LiC(PPh2)(2)(SiMe3), 25, with PCl3 or AsCl3, the triphosphete P-PPh2-C(SiMe3)-PPh2, 26a, or its arsenic analogue As-PPh 2-C(SiMe3)-PPh2, 26b, are respectively formed, along with the chlorine substituted ylide (Cl)(Ph)(2)P=C(PPh2)(SiMe3), 27. 26a,b are characte rized by X-ray structure determinations. The synthesis of the first te n-electron phosphorus cation P[C(PPh2)(2)(SiMe3)](2)(+), 30, with a ho monuclear, spirocyclic PP4-framework was achieved by reacting the trip hosphete 26a with the ylide 27 in the presence of NaBPh4. The crystal structure of the cation of 30, which adopts a Psi-tbp geometry, was de termined.