Structure and reactivity of phosphorus-selenium heterocycles with peri-substituted naphthalene backbones.

Reaction of naphthalene-1.8-bis(dichlorophosphine) with sodium selenide and selenium gives naphthalene-1,8-diyl)-1,3,2,4-diselenoxodiphosphetane 2,4-diselenide (27), a molecule with its four-membered PSePSe ring spanned by a naphthalene-1,8-diyl backbone. 27 was fully characterised, including by X-ray diffraction. Unusually, the reaction yielded not only 27, but also a polymeric or oligomeric material that was selenium deficient, containing significant amount of species with phosphorus atoms not fully oxidised to P(V). Reactions of the selenium deficient material with simple alcohols afforded two 1,2-diphosphaacenaphthenes, which were structurally characterised.

Synthesis and characterisation of four- and six-membered P-Se heterocycles.

The preparation, spectroscopic characterisation and crystal structures of [FcP(mu-Se)Se]2, [FcP(mu-Se2)Se]2 and [PhP(mu-Se2)Se]2 are reported. Crystallographic data reveal planar four-membered PSePSe and skewed six-membered P2Se4 rings, respectively, in all cases with trans arrangement of organic substituents and exo selenium atoms. Whilst stable at room temperature in solid state, NMR data suggest the six-membered rings of both the ferrocenyl and phenyl compounds decompose in the solution with loss of red selenium, forming PSe2PSe five-membered rings.