Oxidation reactions of 1,8‐bis(phosphino)naphthalenes: syntheses and molecular structures of bis(phosphine oxides) and of a bis(phosphine sulfide)

A series of naphthalenediyl-1,8-bis(phosphine oxides) 1-RR′P(:O)(C10H6)-8-P(:O)RR′ (R = R′ = Me (2a), Et (2b), iPr (2c), Cy (2d), Ph (2f) and R = tBu, R′ = Ph (2e) was prepared by oxidation of the corresponding bis(phosphines) 1a–f with molecular oxygen or H2O2·(H2N)2C(:O) and characterized by NMR and IR spectroscopy, mass spectrometry, and elemental analysis (2a, 2b, 2d–f). X-ray crystal structure analyses were performed for 1,8-bis(dimethylphosphinyl)naphthalene (2a), (RR,SS)-1,8-bis(phenyl-tert-butylphosphinyl)naphthalene (2e) and 1,8-bis(diphenylphosphinyl)naphthalene (2f). Treatment of 1,8-bis(diphenylphosphino)naphthalene (dppn, 1f) with an excess of sulfur in hot toluene afforded the bis(phosphine sulfide) 1-Ph2P(:S)(C10H6)-8-P(:S)Ph2 (dppnS2, 3f) the structure of which was elucidated by X-ray crystal structure analysis. The geometries of the compounds 2a, 2e, 2f, and 3f revealed an increase of strain from the corresponding bis(phosphines). In each case, the proximity of the P(:X)R2 groups (X = O, S) led to distortion, the main feature of which was the out-of-plane displacement of the P atoms. © 2001 John Wiley & Sons, Inc. Heteroatom Chem 12:102–113, 2001