Highly fluorous bidentate phosphines

Article abstract of DOI:10.1055/s-2008-1067179

The reaction of tetrachlorodiphosphines [Cl₂P(CH ₂)_nPCl₂; n = 2-4] with fluorous aromatic precursors 4-bromo(perfluorohexyl)benzene and 4-(perfluorohexyl)phenol gave a series of fluorous-tagged diphosphines [(p-C₆F₁₃C ₆H₄)₂P(CH₂)_nP(C ₆H₄C₆F₁₃-p)₂; n = 2-4] and a new diphosphonite [(p-C₆F₁₃C₆H ₄O)₂P(CH₂)₃P(OC₆H ₄C₆F₁₃-p)₂]. The improved synthesis of 1,3-bis(dichlorophosphino)propane (dcpp), involved the facile chlorination of the corresponding primary phosphine with triphosgene. Fluorinated diimines RN=C(CH₃)C(CH₃)=NR, where R = p-C₆H ₄C₆F₁₃ or P-C₆H₄C ₈F₁₇ have also been prepared, and were found to be air-stable alternatives to the highly air-sensitive phosphorus-containing ligands. All compounds were characterised by a variety of techniques including NMR, IR, MS and microanalysis. The successful reduction of the phosphine-oxides [(p-C₆F₁₃C₆H₄)₂P(O) (CH₂)_nP(O)(C₆H₄C₆F ₁₃-p)₂; n = 2,3] with phenylsilane is also presented. Georg Thieme Verlag Stuttgart.

Full text of DOI:10.1055/s-2008-1067179

2626
PAPER
Highly Fluorous Bidentate Phosphines
Highly Fluorous
r
a
e
P
hosphin
des ley M. Berven, George A. Koutsantonis*
Chemistry, School of Biomedical, Biomolecular and Chemical Sciences, University of Western Australia, 35 Stirling Highway,
Crawley 6009, Australia
Fax +08(6488)7247; E-mail: george.koutsantonis@uwa.edu.au
Received 8 April 2008
280 °C, 5 h
Abstract: The
reaction
of
tetrachlorodiphosphines
Cl2P
+
+
4⋅PhPCl2
4⋅PCl3
PCl2
Ph2P
PPh2
[Cl2P(CH2)nPCl2; n = 2–4] with fluorous aromatic precursors 4-bro-
mo(perfluorohexyl)benzene and 4-(perfluorohexyl)phenol gave a
autoclave
1b
series
of
fluorous-tagged
diphosphines
[(p-
Equation 1 Attempted synthesis of 1,3-bis(dichlorophosphino)pro-
pane (1b)
C6F13C6H4)2P(CH2)nP(C6H4C6F13-p)2; n = 2–4] and a new diphos-
phonite [(p-C6F13C6H4O)2P(CH2)3P(OC6H4C6F13-p)2]. The im-
proved synthesis of 1,3-bis(dichlorophosphino)propane (dcpp),
involved the facile chlorination of the corresponding primary phos-
ii
i
iii
phine
with
triphosgene.
Fluorinated
diimines
(EtO)2P
O
P(OEt)2
Br
Br
Cl2P
PCl2
H2P
PH2
RN=C(CH3)C(CH3)=NR, where R = p-C6H4C6F13 or p-C6H4C8F17
have also been prepared, and were found to be air-stable alternatives
to the highly air-sensitive phosphorus-containing ligands. All com-
pounds were characterised by a variety of techniques including
NMR, IR, MS and microanalysis. The successful reduction of the
phosphine-oxides [(p-C6F13C6H4)2P(O)(CH2)nP(O)(C6H4C6F13-p)2;
n = 2,3] with phenylsilane is also presented.
2
1b
O
Scheme 1 Reagents and conditions: (i) P(OEt)3; (ii) LiAlH4, Et2O;
(iii) triphosgene, CH2Cl2.
pursued an alternative approach, which gave 1b in good
yield, by the facile chlorination of 1,3-diphosphinopro-
pane (2) with triphosgene (Scheme 1). Triphosgene
[Cl3COC(O)OCCl3] offers a much safer alternative to
phosgene for the chlorination of PH units, since it is solid
at ambient conditions and can be handled quite easily. A
recent review covers the wide range of applications for
triphosgene in organic synthesis.8 Diphosgene has also
been used to chlorinate 2.9 The synthesis of the primary
phosphine 2 was achieved in two steps; Michaelis–
Arbusov reaction of 1,3-dibromopropane with triethyl-
phosphite,10 followed by reduction of the propylene
diphosphonate with lithium aluminium hydride
(Scheme 1). This method can be employed on scales up to
200 grams. For the chlorination step, it was important to
use a non-nucleophilic solvent such as dichloromethane
because triphosgene was found to react with diethyl ether
to give Cl3COCOOEt.
Key words: fluorous phosphine, scCO2 catalysis, supercritical flu-
ids, copper coupling
Since Horvath and Rabai’s discovery1 that molecules con-
taining greater than 60% by weight in fluorine will sepa-
rate into their own ‘fluorous phase’, there have been
copious new applications of fluorinated compounds in
synthetic chemistry.2,3 Molecules with varying degrees of
fluorination (i.e. below 60% by weight fluorine) can be
separated quite easily on fluorous-reverse-phase-silica-
gel (FRPSG).4 This separation can even be achieved
based on the size, shape and number of fluorous tags in a
compound.3 Furthermore, since highly fluorous mole-
cules exhibit excellent solubility in supercritical CO2
(scCO2), such fluorous molecules have experienced much
current interest. In particular, the ability of highly-fluo-
rous catalysts to separate from the organic substrates and
reaction mixtures in which they are used, is fundamental
to recycling expensive homogeneous catalysts, making
this approach to catalysis more attractive to industry.5
Reaction of the tetrachlorodiphosphines with a suitable
fluorous-tagged aromatic nucleophile would afford our
desired ligands. A survey of the literature revealed a num-
ber of copper-coupling procedures for the synthesis of
fluorous-tagged aryl halides. Lithium–halogen exchange
at the aryl-halide moiety would give the desired aromatic
nucleophiles. We made a detailed study of the conditions
used for the synthesis of the aryl-precursors and made a
number of modifications. The synthesis of the fluorinated
The synthesis of 1,3-bis(dichlorophosphino)propane (1b)
has been reported in the literature by Sommer,6 who
claimed that 1,3-bis(diphenylphosphino)propane (dppp)
could be chlorinated by phosphorus trichloride at 280 °C
in an autoclave (Equation 1).
precursor
4-bromo(perfluorohexyl)benzene
(3;
In our hands, the only identifiable products that were iso-
lated after work-up were PhPCl2 and Ph2PCl, and prob-
lems with this synthesis have been noted by others.7 We
Equation 2)11 was achieved using the substantially cheap-
er benzotrifluoride as an efficient substitute for perfluori-
nated benzene.
The phenol precursor 4-(perfluorohexyl)phenol could be
accessed by a modified copper-coupling procedure report-
ed in the literature.11 Here we found that a reduction in the
SYNTHESIS 2008, No. 16, pp 2626–2630
Advanced online publication: 17.07.2008
DOI: 10.1055/s-2008-1067179; Art ID: Z08208SS
© Georg Thieme Verlag Stuttgart · New York
x
x.
x
x
.
2
0
0
8

PAPER
Highly Fluorous Bidentate Phosphines
2627
Table 1 31P{1H} NMR Shifts of Bidentate Phosphines (ppm)
Br
Br
i
19
Ligand
R = C6H5
–13.2
R = p-C6H4C6F13
–12.5
+
2 CuI
+
C6F13I
R2P(CH2)2PR2
R2P(CH2)3PR2
R2P(CH2)4PR2
C6F13
I
–17.2
–16.5
3
–16.3
–15.3
Equation 2 Reagents and conditions: (i) Cu, DMSO/C6H5CF3, 2,2¢-
bipyridine, 80 °C, 3 d, under argon.
only the corresponding diphosphine oxide/dioxide. It was
found that in solution these ligands were highly sensitive
to oxidation and required rigorous Schlenk techniques in
order to handle them. However, we were able to regener-
ate the diphosphines by reduction of the diphosphine
oxide/dioxide with phenylsilane (PhSiH3); this procedure
is reported in the experimental section.
Cu(s),
ionic liquid*
C6F13
I
I
Br
+
F13C6
Br
80 °C, 20 h
3
* ionic liquid:
N
+
N
Based on NMR and mass spectroscopic evidence, we ob-
served an impurity which formed during the syntheses of
some of the diphosphines that we believe to be a partially
butylated diphosphine arising from reaction of butyllithi-
um with the tetrachlorodiphosphine. This problem was re-
solved by employing a longer lithium–halogen exchange
time.
_
N(SO2CF3)2
Equation 3 Copper coupling in an ionic liquid
Br
i
n
It should also be noted that during column chromatogra-
phy of dfppb (4c) on alumina the ligand oxidized consid-
erably, even under strict Schlenk conditions.
F13C6
P
P
C6F13
2
C6F13
2
4a–c
The reaction of 4-(perfluorohexyl)phenol with a mixture
of triethylamine and 1,3-bis(dichlorophosphino)propane
(1b), gave the diphosphonite dfpop [5; p-
Equation 4 Synthesis of fluorous diphosphines 4a–c. Reagents and
conditions: (i) (a) n-BuLi, –78 °C, Et2O; (b) 1a–c (0.25 equiv),
–78 °C, Et2O.
C6F13C6H4O)2P(CH2)3P(OC6H4C6F13-p)2]. Although
a
near-quantitative yield was obtained, the diphosphonite
was extremely air-sensitive, being susceptible to both ox-
idation of the phosphorus atoms and hydrolysis of the
phosphorus–oxygen bonds.
number of equivalents of copper used, from 4 to 2.5, and
a minor increase (10 °C) in the reaction temperature pro-
vided a three-fold quicker reaction time.
In an effort to further improve the efficiency of these
copper-coupling reactions, particularly the reaction of
4-bromoiodobenzene with perfluorohexyl iodide, we in-
vestigated the use of an ionic liquid as the reaction solvent
(Equation 3). The outcome was an appreciably faster re-
action compared to the DMSO/C6H5CF3 solvent system
used previously. This method, however, was only con-
ducted on a small scale as a trial.
Given the air-sensitivity of these P(III) ligands compared
to their non-fluorous counterparts (e.g. dppe), we sought
other potential ligands that would also impart solubility in
scCO2. a-Diimine ligands 6 and 7 were targeted due to
their good air stability and their application as ligands for
palladium-catalysed polyethylene formation.12–18 The re-
action of fluorous anilines with diacetyl gave the a-di-
imine ligands (Equation 5), albeit in moderate yields.
Spectroscopic monitoring (IR and NMR) indicated that
the unoptimised reaction proceeded slowly to the final di-
imine, with a number of intermediate species still ob-
served in the reaction mixture. A low yield for a similar
analogue has also been reported.14
Lithiation of 3 with butyllithium followed by quenching
with a range of tetrachlorodiphosphines [1a–c; n = 2–4),
gave the diphosphines dfppe (4a; n = 2), dfppp (4b; n = 3)
and dfppb (4c; n = 4), in up to 69% yield (Equation 4).
Although the dfppe analogue 4a (n = 2) has been reported
elsewhere,11 in our hands the reported procedure gave
NH2
O
O
i
+
RF
N
N
+ 2 H2O
RF
RF
R
F = C6F13 (6)
C8F17 (7)
Equation 5 Synthesis of fluorous diimine ligands (6, RF = C6F13; 7, RF = C8F17). Reagents and conditions: (i) camphorsulfonic acid (2%),
5 Å MS, benzene, reflux.
Synthesis 2008, No. 16, 2626–2630 © Thieme Stuttgart · New York

2628
B. M. Berven, G. A. Koutsantonis
PAPER
Table 1 contains the 31P NMR chemical shifts of the fluo-
rous diphosphines compared with their non-fluorous
counterparts. It is clear that the aromatic unit is effective
in insulating the phosphorus atoms from the electron-
withdrawing power of the C6F13 tails but some effect is
distilled from MgSO4 under argon and was stored in the dark at
–25 °C over Ca metal. 1,2-Bis(dichlorophosphino)ethane (1a),
n-BuLi, 4-iodophenol, 2,2¢-bipyridine, lithium bis(trifluoromethyl-
sulfonyl)imide, perfluorohexane, 1,3-dibromopropane and 1,4-di-
bromobutane were used as received. 1,3-Diphosphinopropane (2),20
1,4-bis(dichlorophosphino)butane (1c)21 and 1-butyl-2,2¢-bipyri-
dinium bis(trifluoromethanesulfonyl)amide22 were made according
to published procedures.
1
still observed. The H NMR spectra for all the diphos-
phines show common features in the aromatic region
whilst the bridging protons exhibit similar multiplicities
to those observed for the non-fluorous diphosphine ana-
logues.
In the 13C NMR spectra for all the diphosphines, the C6F13
moieties appear as a series of multiplets over a range of
approximately 8 ppm due to the high degree of carbon–
fluorine coupling. Ligand mass spectra exhibited signals
arising from molecular ions and typical fragmentation
patterns.
4-Bromo(perfluorohexyl)benzene (3)
Method A: To an 80 °C mixture of 4-bromoiodobenzene (10.0 g, 35
mmol), Cu powder (5.0 g, 79 mmol), 2,2¢-bipyridine (0.4 g, 2.5
mmol), C6H5CF3 (60 mL) and DMSO (40 mL) was added a solution
of C6F13I (15.8 g, 35 mmol) in C6H5CF3 (40 mL) dropwise over 2 h.
The mixture was stirred at 80 °C for 72 h then poured into H2O (100
mL). The mixture was filtered through Celite, the solids washed
with C6H5CF3 (50 mL), and the filtrate was poured into a separating
funnel. The lower C6H5CF3 layer was collected and the aqueous lay-
er was back-extracted with additional C6H5CF3 (2 × 50 mL). The
combined C6H5CF3 extracts were then washed with 1M HCl (2 × 50
mL), H2O (3 × 100 mL), then dried over MgSO4 and filtered. Re-
moval of C6H5CF3 on a rotary evaporator afforded a yellow residue
(13.5 g, 79%; by GC this contained 70% 3). This residue was dis-
tilled under vacuum using a Kugelrohr apparatus, affording 3.
In conclusion, we have shown that the synthesis of fluor-
inated diphosphines for potential application in catalysis
is not trivial, given the enhanced air-sensitivity of these
products over the non-fluorous analogues. However, care-
ful optimisation of the copper-coupling conditions has re-
sulted in significant improvements in overall reaction
times and yields compared to established procedures. A
number of new ligands have been prepared and their com-
plexation with metal precursors will appear in another
publication shortly.
Yield: 5.3 g (31%); colourless liquid; bp 70 °C (0.1 mmHg).
1H NMR (600.1 MHz, CDCl3): d = 7.7 (d, 3JH–H = 8.4 Hz, 2 H), 7.5
(d, 3JH–H = 8.4 Hz, 2 H).
MS (EI+): m/z = 474 [M]+.
Method B: To a mixture of 4-bromoiodobenzene (0.28 g, 1 mmol),
activated Cu (64 mg, 1 mmol) and 1-butyl-2,2¢-bipyridinium bis(tri-
fluoromethanesulfonyl)amide (2.9 g) was added C6F13I (0.46 g, 1
mmol). The mixture was stirred at 80 °C for 20 h then cooled to r.t.
and the products were extracted away from the brown ionic liquid
with Et2O (4 × 15mL). The Et2O was removed by rotary evapora-
tion, leaving a cream/brown solid. Upon addition of subsequent
Et2O, this solid separated into its own phase as a yellow liquid. Fur-
ther removal of Et2O regenerated the cream/brown solid (0.64 g,
Manipulation of oxygen- and moisture-sensitive materials was car-
ried out under an atmosphere of high purity argon using standard
Schlenk techniques or in a dry box equipped with removal columns
for H2O (molecular sieves), O2 (CuO) and solvent (activated char-
coal). NMR (1H, 13C, 31P and 19F) spectra were acquired on a Bruker
AM 300 (1H at 300.1 MHz, 13C at 75.5 MHz and 19F at 282.4 MHz),
Bruker ARX 500 (1H at 500.1 MHz, 13C at 125.8 MHz, 31P at 202.5
MHz), or Bruker ARX 600 (1H at 600.1 MHz, 13C at 150.9 MHz,
1
135% mass balance). H NMR analysis of the solid showed it to
contain a mixture of 4-bromoiodobenzene, 3 and residual ionic sol-
vent. GC analysis of the solid indicated a ratio of 32% 3 to 68% 4-
bromoiodobenzene.
1
31P at 242.9 MHz) instruments. H NMR spectra were internally
referenced to residual protonated solvent signals, while 13C NMR
spectra were internally referenced to the 13C resonance of the deu-
terated solvent. 31P NMR spectra were referenced externally to 85%
H3PO4. Chemical shifts (d) are in parts per million (ppm) and quot-
ed coupling constants (J) are given in hertz. Gas chromatography
(GC) experiments were performed on a Hewlett Packard 5890
Series II Gas Chromatograph. Infrared spectra were acquired on a
Biorad FTS 45 Fourier Transform instrument with a resolution of
2 cm–1 unless stated otherwise. Spectra were recorded as KBr discs
or Nujol mulls. Mass spectra were recorded on a VG AutoSpec
spectrometer operating with an 8 kV accelerating voltage in the
FAB+ (fast atom bombardment – positive ion, using nitrobenzyl al-
cohol as the matrix), or EI+ (electron impact – positive ion) mode.
Solvent distillations were conducted under an atmosphere of anhy-
drous, high purity argon. THF and Et2O were pre-dried over sodium
wire and distilled from potassium benzophenone ketyl. Toluene, n-
hexane and dioxane were pre-dried with sodium wire and distilled
from sodium. CH2Cl2, cyclohexane and benzotrifluoride were dis-
tilled from CaH. Acetone was pre-dried with anhydrous CaSO4 and
distilled from this reagent. DMSO was distilled under vacuum and
stored over 4Å MS. Diethylamine was distilled from KOH under an
atmosphere of argon. PCl3 was refluxed under argon for 5 h to re-
move HCl then distilled under argon. 4-Bromoiodobenzene was
sublimed under a static vacuum at 50 °C. Perfluorohexyl iodide and
perfluorooctyl iodide were distilled under argon; n-butyliodide was
4-(Perfluorohexyl)phenol
To a suspension of 4-iodophenol (2.5 g, 11.4 mmol), Cu powder
(1.8 g, 28 mmol) and 2,2¢-bipyridine (0.15 g, 1 mmol) in C6H5CF3
(75 mL) and DMSO (15 mL) at 90 °C was added, dropwise, a solu-
tion of C6F13I (5.0 g, 11.2 mmol) in C6H5CF3 (30 mL) over 2 h. The
mixture was stirred at 90 °C for 55 h then poured into H2O (50 mL).
The resulting mixture was filtered through Celite, the solids washed
with C6H5CF3 (50 mL), and the filtrate poured into a separating fun-
nel. The lower C6H5CF3 layer was collected and the aqueous layer
was back-extracted with additional C6H5CF3 (2 × 50 mL). The com-
bined C6H5CF3 extracts were then washed with 1M HCl (50 mL)
and H2O (50 mL), then dried over MgSO4 and filtered. Removal of
C6H5CF3 on a rotary evaporator afforded a cream solid, which was
recrystallised (n-hexane–CH2Cl2) to give 4-(perfluorohexyl)phenol
as a white crystalline solid (2.1 g, 45%). A further 1.8 g (38%) was
obtained from the filtrate.
3
1H NMR (300.1 MHz, CDCl3): d = 7.5 (d, JH–H = 8 Hz, 2 H), 6.9
(d, 3JH–H = 8 Hz, 2 H), 5.5–5.0 (br, 1 H, OH).
19F NMR (282.4 MHz, CDCl3): d = –81.4 (t, J = 9.0 Hz, 3 F, CF3),
–110.4 (t, J = 14 Hz, 2 F, CF2), –122.1 (m, 2 F, CF2), –122.6 (m,
2 F, CF2), –123.5 (m, 2 F, CF2), –126.8 (m, 2 F, CF2).
Synthesis 2008, No. 16, 2626–2630 © Thieme Stuttgart · New York

PAPER
Highly Fluorous Bidentate Phosphines
2629
1,3-Bis(dichlorophosphino)propane (dcpp; 1b)
MS (FAB+): m/z = 1685 [M]+, 1468 [M – C4F9]+, 1289 [M –
To a solution of 1,3-diphosphinopropane (2; 16 g, 148 mmol) in
CH2Cl2 (500 mL) was added a solution of triphosgene (60 g, 202
mmol) in CH2Cl2 (350 mL) dropwise at –30 °C over 2 h. Effluent
gases were bubbled through two NaOH (0.5M) traps. The solution
was warmed to r.t. with stirring over 12 h, then unreacted triphos-
gene was removed by filtration. The solvent was removed in vacuo,
leaving a cloudy yellow oil, which was fractionally distilled under
vacuum in a short path distillation kit, affording 1b.
C6H4C6F13]+.
(F13C6C6H4)2P(CH2)4P(C6H4C6F13)2 (dfppb; 4c)
To a solution of 3 (4 g, 8.4 mmol) in Et2O (40 mL) at –78 °C was
added n-BuLi (1.6M in n-hexane, 5.6 mL) over 2 h. The reaction
mixture was stirred at –78 °C for 1 h, then 1,4-bis(dichlorophosphi-
no)butane (1c; 0.5 g, 1.9 mmol) dissolved in Et2O–THF (50:50, 70
mL total volume) was added dropwise over 45 min. The mixture
was sustained at –78 °C for 2 h, then allowed to warm to r.t. over 12
h. To the brown suspension was added aq sat. NH4Cl (25 mL, de-
gassed), the organic layer was decanted off and the aqueous layer
was extracted with Et2O (2 × 50 mL). The combined organic ex-
tracts were dried over MgSO4 and filtered [31P NMR of the filtered
solution: 31P{1H} NMR (unlocked in the Et2O–THF mixture): d =
–14.5 (s, 80%, attributed to 4c), –23.5 (m, 20%, suspected butylated
impurity)]. All solvents were removed in vacuo, leaving a brown
oil. To this was added toluene (40 mL) and Et2O (40 mL), which
dissolved most of the oil. Addition of MeCN (80 mL) followed by
cooling to –25 °C for 12 h gave a brown oil beneath a yellow solu-
tion. The supernatant solution was taken and reduced to dryness in
vacuo, affording an orange oil (1.3 g, 41%). Integration of the 31P
NMR spectrum of this oil showed it to contain 4c (28%), suspected
butylated impurities (51%), and oxidised phosphine materials
(21%).
Yield: 31g (84%); colourless oil; bp 82–86 °C (1 mmHg).
1H NMR (500.1 MHz, CDCl3): d = 2.5 (m, 4 H, PCH2), 2.2 (m, 2 H,
CH2).
31P{1H} NMR (202.5 MHz, CDCl3): d = 191.1 (s).
13C{1H} NMR (125.8 MHz, CDCl3): d = 43.0 (dd, JC–P = 46 Hz,
1
3JC–P = 8 Hz, PCH2), 17.1 (t, 2JC–P = 14 Hz, CH2).
(F13C6C6H4)2P(CH2)2P(C6H4C6F13)2 (dfppe; 4a)
To a solution of 3 (5.2 g, 10.9 mmol) in Et2O (50 mL) at –78 °C was
added n-BuLi (1.5M in n-hexane, 7.4 mL, 16.7 mmol) over 2 h. The
reaction mixture was stirred at –78 °C for 1 h, then 1,2-bis(dichlo-
rophosphino)ethane (1a; 0.58 g, 2.5 mmol) in Et2O (25 mL) was
added dropwise over 30 min. The mixture was allowed to warm to
r.t. over 12 h, affording a yellow solution above a white precipitate.
To this was added 10% NH4Cl (50 mL, degassed) with stirring and
the mixture was then transferred to a Schlenk separating funnel. The
organic layer was separated and the aqueous layer was extracted
with Et2O (2 × 50 mL). The combined organic extracts were dried
over MgSO4, filtered and the volume was reduced to 15 mL, giving
an orange solution, which was then cooled to –25 °C. A white pre-
cipitate formed, and the mother liquor was then decanted into anoth-
er flask. The remaining white solid was dried in vacuo, affording 4a.
The brown oil that was beneath the supernatant was dissolved in
C6H5CF3 (10 mL), then subjected to column chromatography on
alumina under argon (Et2O–hexane, 0% then 5%) and the desired
fraction was recrystallised (EtOH) to afford 4c.
Yield: 0.1 g (3%); white powder.
1H NMR (500.1 MHz, CDCl3): d = 7.6 (m, 8 H, Hg), 7.5 (m, 8 H,
Hb), 2.1 (m, 4 H, PCH2), 1.6 (m, 4 H, CH2CH2).
31P{1H} NMR (202.5 MHz, CDCl3): d = –15.3 (s).
13C{1H} NMR (125.8 MHz, CDCl3): d = 143.0 (d, J = 17 Hz, Ca),
132.8 (d, J = 19 Hz, Cb), 129.5 (t, J = 25 Hz, Cw), 126.9 (m, Cg),
121–106 (m, C6F13 tails), 27.2 [m, P(CH2)4P].
Yield: 2.6 g (54%).
1H NMR (300.1 MHz, CDCl3): d = 7.6 (m, 8 H, Hg), 7.4 (m, 8 H,
Hb), 2.2 (virt. t, J = 4.3 Hz, 4 H, CH2CH2).
31P{1H} NMR (202.5 MHz, CDCl3): d = –12.5 (s).
MS (FAB+): m/z = 1670 [M]+.
MS (FAB+): m/z = 1697 [M]+.
(F13C6C6H4)2P(CH2)3P(C6H4C6F13)2 (dfppp; 4b)
Reduction of Phosphine Oxides with Phenylsilane; Typical Pro-
cedure
To a solution of 3 (16.1 g, 33.9 mmol) in Et2O (150 mL) at –78 °C
was added n-BuLi (1.6M in n-hexane, 22.5 mL) in Et2O (50 mL)
over 80 min. The reaction mixture was stirred at –78 °C for 2 h, then
a solution of 1,3-bis(dichlorophosphino)propane (1b; 2.0 g, 8.26
mmol) in Et2O (40 mL) was added dropwise over 90 min. The mix-
ture was allowed to warm to r.t. over 12 h, affording a tan solution
above a white precipitate. To this was added a solution of aq NH4Cl
(10%, 100 mL, degassed) with stirring. The mixture was transferred
to a Schlenk separating funnel, the Et2O layer separated, and the
aqueous layer was extracted with Et2O (3 × 100 mL). The combined
organic extracts were dried over MgSO4, filtered and then reduced
to half the volume in vacuo. After 12 h at –25 °C a white precipitate
formed, which was filtered and washed with Et2O–cyclohexane
(50:50, 2 × 50 mL), then dried in vacuo to give 4b as a white pow-
der (8 g, 58%). Similar treatment of the filtrate yielded further prod-
uct (1.6 g, 11%).
Compound {(F13C6C6H4)2P(O)CH2}2CH2 (4.7 g, 2.74 mmol) and
neat PhSiH3 (8 mL) were heated at reflux for 48 h. Upon cooling,
the translucent mixture formed a white precipitate, which was fil-
tered, washed with cyclohexane (2 × 20 mL) and dried in vacuo to
afford a white solid (2.4 g, 50%). Purification was achieved by re-
crystallisation (Et2O–cyclohexane) to give a white powder, con-
firmed as 4b by 31P and 1H NMR spectroscopy.
(F13C6C6H4O)2P(CH2)3P(OC6H4C6F13)2 (dfpop; 5)
To a solution of 1,3-bis(dichlorophosphino)propane (1b; 0.14 g,
0.57 mmol) dissolved in Et2O (10 mL) was added Et3N (0.35 mL,
2.5 mmol). The reaction mixture was stirred at r.t. for a few minutes,
then a solution of 4-(perfluorohexyl)phenol (1 g, 2.4 mmol) in Et2O
(10 mL) was added dropwise over 30 min. The mixture was stirred
at r.t. for 2 h then filtered through Celite, which was rinsed with
Et2O (100 mL). The filtrate was reduced to dryness in vacuo to give
5.
1H NMR (500.1 MHz CDCl3): d = 7.5 (d, 3JH–H = 8 Hz, 8 H, Hg), 7.4
(virt. t, J = 8 Hz, 8 H, Hb), 2.3 (vt, J = 8 Hz, 4 H, PCH2), 1.6 (m,
2 H, CH2).
31P{1H} NMR (202.5 MHz CDCl3): d = –16.5 (s).
Yield: 0.84 g (84%); pale-yellow oil.
1H NMR (500.1 MHz, C6D6): d = 7.2 (m, 8 H, Hb), 6.8 (m, 8 H, Hg),
2.0 (m, 2 H, CH2), 1.8 (m, 4 H, PCH2).
31P{1H} NMR (125.8 MHz, C6D6): d = 184.2 (s).
13C{1H} NMR (125.8 MHz CDCl3): d = 142.6 (d, JP–C = 17 Hz,
1
Ca), 132.7 (d, 2JP–C = 19 Hz, Cb), 129.6 (t, 2JC–F = 24 Hz, Cw), 126.9
(m, J = 7 Hz, Cg), 119–106 (m, C6F13 tail), 28.9 (t, J = 13 Hz,
PCH2), 22.1 (t, J = 17 Hz, CH2).
Synthesis 2008, No. 16, 2626–2630 © Thieme Stuttgart · New York

2630
B. M. Berven, G. A. Koutsantonis
PAPER
F13C6C6H4N=C(CH3)C(CH3)=NC6H4C6F13 (6)
References
4-(Perfluorohexyl)aniline (0.2 g, 0.49 mmol), diacetyl (0.02 g, 0.24
mmol), camphorsulfonic acid (5 mg), benzene (50 mL) and 5 Å MS
were heated at reflux for 72 h. Volatiles were removed in vacuo,
leaving a brown residue, which was dissolved in EtOH (10 mL).
Cooling to –25 °C gave a yellow precipitate that was filtered to give
6.
(1) Horvath, I. T.; Rabai, J. Science 1994, 266, 72.
(2) Curran, D. P.; Gladysz, J. A.; Horvath, I. T. Handbook of
Fluorous Chemistry; Wiley-VCH: Weinheim, 2004.
(3) Zhang, W.; Curran, D. P. Tetrahedron 2006, 62, 11837.
(4) Curran, D. P.; Hadida, S.; He, M. J. Org. Chem. 1997, 62,
6714.
(5) Ryu, I.; Matsubara, H.; Emnet, C.; Gladysz, J. A.; Takeuchi,
S.; Nakamura, Y.; Curran, D. P. Green Reaction Media in
Organic Synthesis; Blackwell Publishing Ltd.: Oxford, UK,
2005.
Yield: 0.016 g (8%).
1H NMR (500.1 MHz, CDCl3): d = 7.6 (d, J = 8 Hz, 4 H, Ha), 6.9
(d, J = 8 Hz, 4 H, Hb), 2.2 (s, 6 H, CH3).
19F NMR (282.4 MHz, CDCl3): d = –77.2 (t, J = 10 Hz, 6 F, CF3),
–106.5 (t, J = 14 Hz, 4 F, CF2Ar), –117.9 (br, 4 F, CF2), –118.3 (br,
4 F, CF2), –119.2 (br, 4 F, CF2), –122.6 (br, 4 F, CF2).
(6) Sommer, V. K. Z. Anorg. Allg. Chem. 1970, 376, 37.
(7) Diemert, K.; Kuchen, W.; Kutter, J. Chem. Ber. 1982, 115,
1947.
(8) Cotarca, L.; Delogu, P.; Nardelli, A.; Sunjic, V. Synthesis
1996, 553.
(9) Lindner, E.; Schmid, M.; Wald, J.; Queisser, J. A.; Geprags,
M.; Wegner, P.; Nachtigal, C. J. Organomet. Chem. 2000,
602, 173.
F17C8C6H4N=C(CH3)C(CH3)=NC6H4C8F17 (7)
4-(Perfluorooctyl)aniline (1.0 g, 1.96 mmol), diacetyl (0.084 g, 0.98
mmol), camphorsulfonic acid (45 mg) and benzene (120 mL) were
heated at reflux with an attached Soxhlet extractor containing 5 Å
MS, for 72 h. Volatiles were then removed in vacuo, leaving a
brown residue to which was added MeOH (100 mL). Heating to
boiling point resulted in the formation of a brown solution with a
permanently insoluble tan solid. The suspension was cooled to r.t.
and filtered to obtain 7 as a tan solid.
(10) Griffith, J. A.; McCauley, D. J.; Barrans, R. E. Jr.; Herlinger,
A. W. Synth. Commun. 1998, 28, 4317.
(11) Bhattacharyya, P.; Gudmunsen, D.; Hope, E. G.; Kemmit, R.
D. W.; Paige, D. R.; Stuart, A. M. J. Chem. Soc., Perkin
Trans. 1 1997, 3609.
(12) Bahuleyan, B. K.; Son, G. W.; Park, D.-W.; Ha, C.-S.; Kim,
I. J. Polym. Sci., Part A: Polym. Chem. 2008, 46, 1066.
(13) Brookhart, M.; Ittel, S. D.; Johnson, L. K. Chem. Rev. 2000,
100, 1169.
(14) Popeney, C. S.; Guan, Z. Organometallics 2005, 24, 1145.
(15) Rosa, V.; Carabineiro, S. A.; Aviles, T.; Gomes, P. T.;
Welter, R.; Campos, J. M.; Ribeiro, M. R. J. Organomet.
Chem. 2008, 693, 769.
(16) Kiesewetter, J.; Arikan, B.; Kaminsky, W. Polymer 2006,
47, 3302.
Yield: 0.19 g (18%).
1H NMR (500.1 MHz, acetone-d6): d = 7.7 (d, J = 8 Hz, 4 H, Ha),
7.1 (d, J = 8 Hz, 4 H, Hb), 2.2 (s, 6 H, CH3).
13C{1H} NMR (125.8 MHz, acetone-d6): d = 169.3 (s, C=N), 155.7
(s, Ca), 128.8 (t, J = 6 Hz, Cg), 123.8 (m, Cw), 119.9 (s, Cb), 15.6 (s,
CH3); the fluorous tag was not observed due to the low sample con-
centration.
MS (FAB+): m/z = 1073 [M]+, 536 [M – C10F22]+.
IR (nujol): 1682 (C=N) cm–1.
(17) Rose, J. M.; Cherian, A. E.; Coates, G. W. J. Am. Chem. Soc.
2006, 128, 4186.
(18) Brookhart, M.; Gottfied, A. C. Macromolecules 2003, 36,
3085.
Anal. Calcd for C32H14F34N2: C, 35.84; H, 1.32; N, 2.61. Found: C,
36.14; H, 1.49; N, 2.87.
(19) Tebby, J. C. Handbook of Phosphorus-31 Nuclear Magnetic
Resonance Data; CRC Press: Boca Raton, 1991.
(20) Taylor, C. R.; Walters, D. B. Inorg. Synth. 1973, 14, 10.
(21) Diemert, K.; Kuchen, W.; Kutter, J. Phosphorus and Sulfur
1983, 15.
Acknowledgment
We thank the University of Western Australia for partial funding of
this work. B.M.B. was a holder of an Australian Postgraduate
Award.
(22) Xiao, J.; Ye, C.; Shreeve, J. M. Org. Lett. 2005, 7, 1963.
Synthesis 2008, No. 16, 2626–2630 © Thieme Stuttgart · New York