Abstract:
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.
