1,5-Diphosphabicyclo[3.3.1]nonan

1,5-Diphosphabicyclo [3.3.1]nonane 1,5-Diphosphabicyclo[3.3.1]nonane 8 has been obtained by free-radical cyclization of CH₂?CHCH₂(H)PCH₂P(H)CH₂CH?CH₂ 6 and 1-allyl-1,3-diphosphorinane 7 . For the synthesis of 6 and 7 the chlorophosphine Cl₂PCH₂PCl₂ 1 is used as a starting material, which can be converted into Me₂N(Cl)PCH₂P(Cl)NMe₂ 3 by reaction with (Me₂N)₂PCH₂P(NMe₂)₂ 2 . Treatment of 3 with two equivalents of allyl lithium and cleavage of the PN bonds in CH₂?CHCH₂(Me₂N)PCH₂P(NMe₂)CH₂CH?CH₂ 4 with diluted HCl affords CH₂?CHCH₂(H)(O)PCH₂P(O)(H)CH₂CH?CH₂ 5 . Phenylsilane is used for the first time as a reducing agent to obtain a secundary phosphine like 6 from the secundary phosphine oxide ( 5 ). Prolonged heating increases the yield of the byproduct 7 in the mixture of 6 and 7 . Reactions of the trivalent phosphorus in 8 with CS₂, CH₃I, POCl₃, NO, sulfur, and KSeCN, respectively, delivers the corresponding derivatives 9–17 . The compounds decribed are characterized by ¹H, ¹³C, ³¹P, ⁷⁷Se n.m.r., i.r., and m.s. data.