Reduction reactions of a 1,3,5-triphosphabenzene

Abstract

The reactions of the triphosphabenzene, 1,3,5-P₃C₃Bu^t₃, with LiMH₄, M = Al or Ga, lead to the triphosphabicyclo[3.1.0]hexanediyl metallate complexes, [{[Li(OEt₂)][MH₂(P₃C₃Bu^t₃H₂)]}₂], which give exo- and endo-isomers of a triphosphabicyclo[3.1.0]hexane, P₃C₃Bu^t₃H₄ upon quenching. The related reaction of [AlH₃(NMe₃)] with 1,3,5-P₃C₃Bu^t₃ affords three identifiable products, viz. a triphosphabicyclo[3.1.0]hexenyl complex, [AlH₂(P₃C₃Bu^t₃H)(NMe₃)], and two triphosphabicyclo[3.1.0]hexanediyl complexes, [AlH(P₃C₃Bu^t₃H₂)(NMe₃)] and [Al₂H₄(P₃C₃Bu^t₃H₂)(NMe₃)]. In contrast, the reactions of 1,3,5-P₃C₃Bu^t₃ with either [GaH₃(quin)], quin = quinuclidine, or Me₃SnH lead only to the triphosphabicyclo[3.1.0]hexenyl complexes, [GaH₂(P₃C₃Bu^t₃H)(quin)] and [Me₃Sn(P₃C₃Bu^t₃H)]. Quenching of the former affords a triphosphabicyclo[3.1.0]hexene, P₃C₃Bu^t₃H₂, while quenching the latter gives its triphosphacyclohexa-1,4-diene valence isomer. Treatment of 1,3,5-P₃C₃Bu^t₃ with “GaI” yields a GaI₃ complex of the triphosphahexa-1,4-diene, [GaI₃(P₃C₃Bu^t₃H₂)], whilst treatment with the anionic Ga(I) heterocycle, [:Ga{N(Ar)C(H)}₂]⁻, Ar = C₆H₃Prⁱ₂-2,6, affords the known diphospholyl anion, [1,3-P₂C₃Bu^t₃]⁻via a P-abstraction from the triphosphabenzene. Finally, reaction of the 1,3,5-triphosphacyclohexane, {P(OEt)C(H)(Bu^t)}₃, with thionyl chloride yields the unusual λ⁵,λ⁵,λ⁵-1,3,5-triphosphacyclohexane, {P(O)(Cl)C(H)(Bu^t)}₂{P(OEt)(S)C(H)(Bu^t)}. Suggestions as to the mechanisms of a number of these reduction reactions are made and the crystal structures of seven compounds are reported.