Phosphinomethanides and Group 15 element halides: Redox reactions, rearrangements and novel heterocycles

Abstract

The reactions of ECl 3 (E = P, As, Sb, Bi), RPCl 2 (R = Me, Ph, tBu, Cy 2N) and Ph 2PCl, respectively, with ambident lithium phosphinomethanides are described. The reaction with LiCH 2PMe 2, 1, by E C bond formation, leads to the substitution products E(CH 2PMe 2) 3, 2a–d, (E = P, As, Sb, Bi) and R—P(CH 2PMe 2) 2 (R = Me, Ph, tBu, Cy 2N) 5a–d. In contrast, LiC(PMe 2)(SiMe 3) 2 · 0.5TMEDA, 6, gives substitution products with ECl 3 (E = P, As, Sb), by E P bond formation. Thus, the first element—tris(P—ylide)derivatives E(PMe 2 C(SiMe 3) 2) 3, 7a–c, are obtained. 7b is characterized by X-ray structure determination. In these reactions, oxidative P P coupling to give [(Me 3Si) 2C PMe 2] 2, 8, is also observed, and exclusively in the reaction of BiCl 3 with 6. The reaction of RPCl 2 (R = Me, Ph, tBu, Cy 2N) with 6 strongly is dependent on the nature of R. For R = Me, only substitution is observed, yielding Me P(PMe 2 C(SiMe 3) 2) 2, 10, while for R = Ph, both substitution and Li/Cl exchange with subsequent formation of 8 and the diphosphane [(Me 3Si) 2C PMe 2 PPh] 2, 12, are found. The latter has been characterized structurally. In contrast, for R = tBu, only ( tBuP) 3, 13, and ( tBuP) 4, 14, are obtained. An analogous result is observed in the reaction of tBuPCl 2 with LiC(PMe 2) 2(SiMe 3), 17. The reaction of Cy 2NPCl 2 with two equivalents of LiC(PMe 2)(SiMe 3) 2·0.5TMEDA, 6, gives a phospha-alkene Cy 2N P C(SiMe 3) 2, 16, and the substitution product Cy 2N P(PMe 2 C(SiMe 3) 2) 2, 15. Likewise, LiC(PMe 2) 2(SiMe 3), 17, reacts with PhPCl 2 to give the substitution product Ph P(PMe 2 C(PMe 2)(SiMe 3)) 2, 18, which is characterized by X-ray structure determination, whereas with MePCl 2 only the P—ylide Me 2P PMe 2 C(PMe 2)(SiMe 3), 20, and the coupling product [(Me 2P)(Me 3Si)C PMe 2] 2, 19, are formed. The latter is also obtained in the reactions of BiCl 3 or SbCl 3 with LiC(PMe 2) 2(SiMe 3), 17. Analogous redox reactions with AsCl 3 and PCl 3, respectively, lead to the bis-pentacyclic μ-[C(PMe 2) 2(SiMe 3)]As 2 2, 21, and the hexacycle P − PMe 2 − C(SiMe 3 ) − PMe 2 − C(SiMe 3 ) − ⎴ PMe 2 , 22, which were structurally characterized by X-ray analyses. Depending on the reaction conditions, the reaction of PCl 3 with LiC(PMe 2) 2(SiMe 3), 17, alternatively may lead to the triphosphete P − PMe 2 − C(SiMe 3 ) − ⎴ PMe 2 , 24. By using P—phenyl-substituents instead of P—methyl-substituents, i.e. in the reaction of LiC(PPh 2) 2(SiMe 3), 25, with PCl 3 or AsCl 3, the triphosphete P − PPh 2 − C(SiMe 3 ) − ⎴ PPh 2 , 26a, or its arsenic analogue As − PPh 2 − C(SiMe 3 ) − ⎴ PPh 2 , 26b, are respectively formed, along with the chlorine substituted ylide (Cl)(Ph) 2P C(PPh 2)(SiMe 3), 27. 26a,b are characterized by X-ray structure determinations. The synthesis of the first ten-electron phosphorus cation P[C(PPh 2) 2(SiMe 3)] 2 +, 30, with a homonuclear, spirocyclic PP 4-framework was achieved by reacting the triphosphete 26a with the ylide 27 in the presence of NaBPh 4. The crystal structure of the cation of 30, which adopts a Ψ-tbp geometry, was determined.