Some pentafluorophenyl derivatives of selenium

Abstract

The preparations of a number of pentafluorophenyl derivatives of selenium are described. Reactions of transition metal ions with excess of the anion C₆F₅Se⁻ in aqueous solution generally give complex ions of the type [M(SeC₆F₅)x]y⁻ but sometimes only simple salts of the type M(SeC₆F₅)₂ are obtained. The electronic spectra of these compounds are discussed. The ligand C₆F₅Se has been incorporated into transition metal organometallic compounds giving the derivatives (π-C₅H₅)Fe(CO)₂SeC₆F₅, {(π-C₅H₅)NiSeC₆F₅}n, (π-C₅H₅)Ni(PPh₃)SeC₆F₅, C₆F₅SeMn(CO)₅ and C₆F₅SeRe(CO)₅. Unsymmetrical selenides, C₆F₅SeR, where the substituents, R, are various alkyl and aryl groups, are prepared by a variety of methods. Preparations of the compounds C₆F₅SeN(CH₃)₂, C₆F₅SeN(C₂H₅)₂, (C₆F₅Se)₂NH and C₆F₅SeOCH₃ are also described. The preparations of various penta-fluorophenyl derivatives of higher valent selenium are attempted resulting in the formation of the compounds C₆F₅SeCl₂CH₃, C₆F₅SeCl₂C₆H₅, C₆F₅Se(O)C₆H₅, (C₆F₅SeO)₂O and C₆F₅Se(O)Cl. No pentafluorophenyl derivatives of six valent selenium are obtained. Vibrational spectra of the compounds prepared are briefly discussed and SeO stretching mode assignments made. ¹⁹F n.m.r. spectra are also discussed. -- The properties of pentafluorophenyl derivatives of selenium are compared with those of organoselenium compounds, particularly perfluoroalkyl derivatives of selenium, and with pentafluorophenyl derivatives of sulphur.