Studies of nucleophilic attack on tris (pentafluorophenyl) phosphine and its oxides

The reaction of tris(pentafluorophenyl)phosphine [5] with the nucleophiles dimethyl formamide (DMF), hexamethylphosphoric triamide (HMPA), diethyl formamide (DEF), hexaethylphosphoric triamide (HEPA), hydrazine, N,N-dimethyl hydrazine (in presence and/or absence of KF), phenylhydrazine, ammonium hydroxide, formamide, aniline, sodium hydrogen sulfide, and hexaethylphosphorous triamide was investigated. The reaction of [5] with DMF and HMPA gave the same product, namely tris-[4-(N,N-dimethylamino)-2,3,5,6-tetrafluorophenyl]phosphine [12] but in higher yield in the case of HMPA. Compound (5] also reacted with DEF to give tris[4-(N,N-diethylamino)-2,3,5,6-tetrafluorophenyl] phosphine [14]. When [51 was treated with HEPA, it gave a mixture of bis(pentafluorophe~yl)-(N,N-diethylamino-tetrafluorophenyl)phosphine, pentafluorophenyl-bis-(N,N-diethylamino-tetrafluorophenyl)phosphine and tris (N,N-diethylamino-tetrafluorophenyl)phosphine. Treatment of [5] with aqueeus hydrazine solution in excess ethanol gave tris(4-hydrazo-2,3,4,6-tetrafluorophenyl)phosphine [1s1 in high yield while reaction with aqueous hydrazine led to C-P cleavage and production of tetrafluorophenyl hydrazine. With N,N-dimethyl hydrazine, [5] gave tris(4-N,N-dimethylhydrazine-2,3,5,6-tetrafluorophenyl) phosphine {20j. The latter could be obtained in higher yield and shorter reaction time, by the addition of KF. The reaction of compound {51 with phenylhydrazine in THF gave bis(pentafluorophe~yl)-4-S-phenylhydrazino- 2,3,5,6-tetrafluorophenyl phosphine [22] in low yield. Reaction of [5] with ammonium hydroxide in THF at high pressure in the presence of KF gave tris-~4-amino-2,3,5,6-tetrafluorophenyl)phosphine [25]. Similarly, formamide led to a mixture of (C6F4NHZ)3P, (C6F4NHZ)ZPC6FS, (C6F4NHZ)ZPC6F4NHCHO, and C6F4NHZP(C6Fs)(C6F4NHCHO). When [5] was treated with aniline, a mixture of mono-, di-, and tri-substituted products was obtained. Sodium hydrogen sulfide in ethylene glycol/ pyridine led to C-P cleavage and the isolation of pentafluorobenzene and tetrafluorothiophenol. Reaction of [5] and its oxide [35] with different alkoxides in the corresponding alcohols led mainly to C-P bond cleavage products, with the exception of one case where sodium methoxide was used in ether, and which led to tris-(4-methoxy-2,3,9,6-tetrafluorophenyl)phosphine [37]. On the basis of various spectroscopic data, it was concluded that the para position in compound [5] was generally the favoured site of attack.

Infrared Spectroscopy of Gadolinium

Measurements of the optical reflectivity of the normal incident light along c-axis [0001] have been made on a Gadolinium single crystal, for temperatures between 50 K and room temperature just above the Curie temperature of Gd, which is 293 K. And covering the spectrum range between 100 -11000 cm-I . This work is the first study of Gd in the far infrared range. In fact it fills the gap below 0.2 eV which has never been measured before. Extreme attention was paid to the fact that Gadolinium is a very reactive metal with air. Thus, the sample was mechanically polished and carefully handled during the measurement. However, temperature dependent optical measurements have been made in the same frequency range for a sample of Gd2O3. For comparison, both samples of Gd and Gd2O3 were examined by X-Ray diffraction. XRD analysis showed that the sample was pure gadolinium and the oxide layer either does not exist, or is very thin. Furthermore, this fact was supported by the absence of any of Gd2O3 features in the Gd sample reflectivity. Kramers Kronig analysis was applied to extract the optical functions from the reflectance data. The optical conductivity shows a strong temperature dependence feature in the mid-infrared. This feature disappears completely at room temperature which supports a magnetic origin.