Heterocycle formation using [PhP(Se)(μ-Se)]2. The crystal structures of [PhP(Se)(μ-Se)]2, PhP(Se)Se2(C7H10) and PhP(Se)(μ-Se)(μ-NPh)P(Se)Ph

Abstract

An X-ray crystallographic study of [PhP(Se)(μ-Se)]₂1, the oxidation product of the homocycle (PhP)₅ with ten equivalents of selenium, revealed that the molecule is centrosymmetric with a planar central P₂(μ-Se)₂ core and trans disposition of exocyclic PSe bonds. In the reaction of 1 with norbornene (bicyclo[2.2.1]hept-2-ene), crystallographic analysis of the product 2 revealed exo addition of a PhP(Se)Se₂ unit across the CC bond, giving a 1,2-diselena-3-phospholane (C₂PSe₂) ring. Norbornadiene (bicyclo[2.2.1]hepta-2,5-diene) reacts more slowly with 1, allowing the isolation of a 1,2-selenaphosphetane (C₂PSe ring) in addition to a diselenaphospholane. The reaction of 1 with azobenzene proceeds with cleavage of the NN bond and substitution of a bridging selenium atom in 1 by an NPh unit, giving the first crystallographically characterised selenaazadiphosphetane (P₂SeN) ring.