Highly fluorous derivatives of 1,2-bis(diphenylphosphino)ethane

Full text of DOI:10.1021/jo000312k

5424
J . Org. Chem. 2000, 65, 5424-5427
their nonfluorous counterparts. The weakly electron-
High ly F lu or ou s Der iva tives of
1,2-Bis(d ip h en ylp h osp h in o)eth a n e
donating character of the silyl substituent, which com-
pensates for the electron-withdrawing effect of the per-
fluoroalkyl tail, is most probably responsible for this
retention of catalytic activity. An additional advantage
of the -CH2CH2SiR2-spacer is the possibility to connect
multiple (up to three) perfluorotails per aryl ring via the
Si-center through straightforward synthetic methodolo-
gies.9,11 This latter characteristic allows the synthesis of
ligands and derived transition metal complexes with high
fluorphase affinity. Application of these ligands in fluo-
rous biphasic metal-catalyzed organic synthesis is ex-
pected to result in improved catalyst recycling.
Elwin de Wolf,† Bodo Richter,†
Berth-J an Deelman,*,‡ and Gerard van Koten†
Debye Institute, Department of Metal-Mediated
Synthesis, Utrecht University, Padualaan 8,
3584 CH Utrecht, The Netherlands, and Elf
Atochem Vlissingen B.V., P.O. Box 70,
4380 AB Vlissingen, The Netherlands
b.j.deelman@chem.uu.nl
Received March 6, 2000
The fact that monophosphines are known to dissociate
easily from the metal center under catalytic conditions
may result in leaching of the free fluorous ligand into
the organic phase.9d To counteract this obvious disad-
vantage of the use of monophosphines in catalysis,
chelating diphosphines have found widespread applica-
tion in transition metal-based homogeneous catalysis.12
Two fluorous examples of 1,2-bis(diphenylphosphino)-
ethane (dppe) containing four perfluorotails (1 and 2)
were recently reported.4a,5 However, studies which em-
ploy 1 in fluorous biphasic catalysis have not been
reported. Diphosphine 2 was applied in fluorous biphasic
hydrogenation of styrene, using [Rh(µ-Cl)2(2)]2 as cata-
lyst.13 The activity of this system, however, was modest
in comparison with the more commonly used [Rh(diene)-
(diphosphine)]+ systems.12,14 Since diphosphine catalysts
which combine high fluorous phase retention with high
catalytic activity have not been reported yet, we have now
employed silyl spacers to prepare highly fluorous deriva-
tives of dppe, stimulated by the positive results obtained
for fluorous triarylphosphines. The synthetic results
along with some quantitative solubility studies of the
diphosphines are presented below.
In tr od u ction
Since the first demonstration of catalyst recovery using
the technique of fluorous biphasic separation,1 several
classes of ligands have been functionalized with perfluo-
roalkyl chains to increase solubility of these ligands and
derived catalysts in fluorous solvents.2 Published work
concerning phosphorus ligands has been mainly focused
on fluorous versions of monodentate tertiary phosphines
which contain hydrocarbon spacers to insulate the phos-
phorus atom from the electron-withdrawing effect of the
perfluoroalkyl tails.3 Triarylphosphines with perfluoro-
tails directly connected to the aryl ring4 and through a
-CH2CH2- spacer5 as well as perfluoroalkylated phos-
phinites, -phosphonites,6 and -phosphites7 have been
prepared. However, performance of these ligands in
catalysis is often lower compared with conventional
nonfluorous ligands.
To counteract this drop in activity upon fluorotail
functionalization, we introduced the -CH2CH2SiR2-
spacer (R ) Me or -CH2CH2CmF2m+1) to prepare fluorous
2,6-bis[(dimethylamino)methyl]arylnickel- and plati-
num-,8 fluorous triarylphosphine rhodium,9 and chiral
arenethiolate zinc complexes10 containing perfluoroalkyl
tails. All of these catalysts displayed similar activity as
† Debye Institute.
‡ Elf Atochem, currently based at the Debye Institute. Fax: +31 30
252 3615.
(1) Horva´th, I. T.; Ra´bai, J . Science 1994, 266, 72-75.
(2) (a) De Wolf, E.; Van Koten, G.; Deelman, B.-J . Chem. Soc. Rev.
1999, 28, 37-41. (b) Horva´th, I. T. Acc. Chem. Res. 1998, 31, 641-
650. (c) Curran, D. P. Angew. Chem., Int. Ed. 1998, 37, 1174-1196.
(d) Cornils, B. Angew. Chem., Int. Ed. Engl. 1997, 36, 2057-2059. (e)
Hope, E. G.; Stuart, A. M. J . Fluorine Chem. 1999, 100, 75-83.
(3) (a) Horva´th, I. T.; Kiss, G.; Cook, R. A.; Bond, J . E.; Stevens, P.
A.; Ra´bai, J .; Mozelski, E. J . J . Am. Chem. Soc. 1998, 120, 3133-3143.
(b) Sinou, D.; Pozzi, G.; Hope, E. G.; Stuart, A. M. Tetrahedron Lett.
1999, 40, 849-852. (c) Alvey, L. J .; Rutherford, D.; J uliette, J . J . J .;
Gladysz, J . A. J . Org. Chem. 1998, 63, 6302-6308. (d) Klose, A.;
Gladysz, J . A. Tetrahedron: Asymmetry 1999, 10, 2665-2674. (e)
J uliette, J . J . J .; Rutherford, D.; Horva´th, I. T.; Gladysz, J . A. J . Am.
Chem. Soc. 1999, 121, 2696-2704.
Resu lts a n d Discu ssion
Starting compound 1,2-bis[bis(4-bromophenyl)phos-
phino]ethane (3) was easily obtained by addition of 1,2-
bis(dichlorophosphino)ethane to a suspension of p-BrC6H4-
(4) (a) Bhattacharyya, P.; Gudmunsen, D.; Hope, E. G.; Kemmitt,
R. D. W.; Paige, D. R.; Stuart, A. M. J . Chem. Soc., Perkin Trans. 1
1997, 3609-3612. (b) Betzemeier, B.; Knochel, P. Angew. Chem., Int.
Ed. Engl. 1997, 36, 2623-2624.
(5) Kainz, S.; Koch, D.; Baumann, W.; Leitner, W. Angew. Chem.,
Int. Ed. Engl. 1997, 36, 1628-1630.
(9) (a) Richter, B.; De Wolf, A. C. A.; Van Koten, G.; Deelman, B. Y.
PCT Int. Appl. WO 0018444, 2000, to Elf Atochem. (b) Richter, B.; Van
Koten, G.; Deelman, B.-J . J . Mol. Catal.(A), Chem. 1999, 145, 317-
321. (c) Richter, B.; De Wolf, E.; Van Koten, G.; Deelman, B.-J . J . Org.
Chem. 2000, 65, 3385-3893. (d) Richter, B.; Spek, A. L., Van Koten,
G.; Deelman, B.-J . J . Am. Chem. Soc., 2000, 122, 3945-3951.
(10) Kleijn, H.; Rijnberg, E.; J astrzebski, J . T. B. H.; Van Koten, G.
Org. Lett. 1999, 1, 853-855.
(6) Haar, C. M.; Huang, J .; Nolan, S. P.; Petersen, J . P. Organome-
tallics 1998, 17, 5018-5024.
(7) Mathivet, T.; Monflier, E.; Castanet, Y.; Morteaux, A.; Couturier,
J .-L. Tetrahedron Lett. 1998, 39, 9411-9414.
(8) Kleijn, H.; J astrzebski, J . T. B. H.; Gossage, R. A.; Kooijman,
H.; Spek, A. L.; Van Koten, G. Tetrahedron 1998, 54, 1145-1152.
10.1021/jo000312k CCC: $19.00 © 2000 American Chemical Society
Published on Web 07/28/2000

Notes
J . Org. Chem., Vol. 65, No. 17, 2000 5425
Sch em e 1
Li in a 3:1 (v/ v) mixture of hexane and ether (Scheme
1). The fluorinated dppe derivatives 4a -d were formed
after lithiation of 3 in THF at -90 °C followed by coupling
with silyl halides (RfCH2CH2)nSiMe3-nX (Rf ) C6F13 or
C8F17; X ) Cl or Br).9 The products were isolated as air-
stable15 white solids (4a and 4d ) or colorless to yellow
oils (4b and 4c) in high yields. Using a similar synthetic
route, nonfluorous 1,2-bis[bis{4-(trimethylsilyl)phenyl}-
phosphino]ethane (4e) was synthesized for comparison.
The fluorous silyl bromides (RfCH2CH2)nSiMe3-nBr
(n ) 2, 3) often contain some Wurtz-coupling product,
(RfCH2CH2)2.9c Since this side product was difficult to
remove, the crude fluorous silyl bromides were used
without further purification. It appeared that once the
fluorous silyl bromides had been converted to the diphos-
phines 4b or 4c, the Wurtz-coupling product was easily
removed by Kugelrohr distillation (4b) or washing with
pentane (4c). Since RfCH2CH2SiMe2Cl (Rf ) C6F13 or
C8F17) was obtained by hydrosilylation, this extra puri-
fication procedure was not necessary in the synthesis of
4a and 4d .
as the ipso-, o-, and m-phenyl carbons (relative to
phosphorus) of phosphines 3, 4a , and 4e are observed as
the X part of an ABX spin system in the 13C NMR
spectrum.17 These observations are in close agreement
with those for dppe itself.18
Comparison of the 31P chemical shifts of dppe (δ )
-11.1) and 4a -e in C6D6/C6F6 (1:1 by volume) shows a
small high field shift for 4a -e (δ ) -11.3 to -11.4). With
some caution, it can be concluded that this is mainly
caused by the p-silyl substitution and that the silicon
spacer is indeed a good insulator for the electron-
withdrawing effect of the perfluorotail.9
Attaching p-SiMe3 groups to the aryl rings of dppe, as
in 4e, results in a large increase of the melting point
(Table 1). However, when four CH2CH2C6F13 or CH2-
CH2C8F17 tails are connected (4a and 4d ), the diphos-
phines melt at lower temperature than 4e. Compound
4d melts at higher temperature than 4a , possibly due to
the higher molecular weight. Similar trends in melting
points were observed for related fluorous triphenylphos-
phine derivatives.9 The dppe derivatives containing 8 or
12 fluorotails (4b and 4c) did not solidify at room
temperature.
The phosphines 3 and 4a -e were identified by both
1H and 31P NMR spectroscopy and elemental analyses.
Compounds 4a and 4d were further characterized by
their 19F NMR data and 3, 4a , and 4e by 13C NMR
spectroscopy. All spectral data corresponded to the
proposed structures and no partly substituted products,
bearing less than four SiMe3-n(CH2CH2Rf)n groups, were
observed. The PCH2CH2P signal, which usually appears
Solubility data for the new perfluoroalkylated dppe
derivatives were obtained in THF, toluene, and PFMCH
(Table 1). A large difference in solubility between 4a and
4d was observed; the derivative with the shorter tail (4a )
is soluble in both polar (THF, CH2Cl2) and aromatic
organic solvents (toluene and benzene) whereas solubility
in PFMCH is low. The phosphine containing the longer
fluorotail (4d ) is poorly soluble in both aromatic solvents
and PFMCH. Interestingly, it is moderately soluble in
amphiphilic media like CF3C6H5 and mixtures of benzene
and hexafluorobenzene of different ratios.19
1
as a pseudo or virtual triplet in the H NMR spectrum,4a,16
was observed as a shoulder on the -CH2CF2- signal for
4a -d .
The methylene carbons of the PCH2CH2P unit as well
From Table 1 it is clear that the solubility of dppe in
(11) (a) Struder, A.; Curran, D. P. Tetrahedron 1997, 53, 6681-6696.
(b) Struder, A.; J eger, P.; Wipf, P.; Curran, D. P. J . Org. Chem. 1997,
62, 2917-2924.
(12) See for example: Brunner, H. In Applied Homogeneous Ca-
talysis with Organometallic Compounds; Cornils, B., Herrmann W. A.,
Eds.; VCH: Weinheim, 1996; Chapter 2.2, pp 201-219.
(13) Hope, E. G.; Kemmitt, R. D. W.; Paige, D. R.; Stuart, A. M. J .
Fluorine Chem. 1999, 99, 197-200.
(14) Schrock, R. R.; Osborn, J . A. J . Am. Chem. Soc. 1976, 98, 4450-
4455.
(15) No oxidation products were observed after exposing a toluene
solution of 4b to air for 3 days.
(16) See for example in (a) Casey, C. P.; Paulsen, E.; Beuttenmueller,
E. W.; Proft, B. R.; Petrovich, L. M.; Matter, B. A.; Powell, D. R. J .
Am. Chem. Soc. 1997, 119, 11817-11825. (b) Casey, C. P.; Bullock, R.
M.; Nief, F. J . Am. Chem. Soc. 1983, 105, 7574-7580. (c) Brunner,
H.; J anura, M.; Stefaniak, S. Synthesis 1998, 1742-1749.
2
(17) For the methylene carbons the sum of 1J PC and J PC is close to
zero, resulting in a singlet (4a and 4e, 1J PC + 2J PC < 1 Hz) or a doublet
(3, 1J PC + 2J PC ) 2 Hz) for these carbon signals. The ipso- and o-phenyl
carbons are observed as triplets. Satellites on the triplet of the
3
o-carbons allowed the determination of J PP (36 Hz) by spectral
simulation. No or little second-order effects were observed on the
m-carbon signals of 4a and 4e, whereas a triplet was observed for 3,
3
indicating a smaller J PC for the former compounds.
(18) King, R. B.; Cloyd, J . C. J . Chem. Soc., Perkin Trans 2 1975,
938-941.
(19) Attemps to synthesize a (C8F17CH2CH2)2MeSi-substituted de-
rivative of dppe (n ) 2; Rf ) C8F17) gave the desired product. Although
its purification was severely hindered by the low solubility, the crude
product showed a similar behavior in PFMCH as 4d .

5426 J . Org. Chem., Vol. 65, No. 17, 2000
Ta ble 1. P h ysica l P r op er ties of 4a -e a n d Dp p e
Notes
solubilitya
compound
THF
(mmol/L)
toluene
PFMCH
(mmol/L)
entry
Rf
n
wt % F
(g/L)
(g/L)
(mmol/L)
(g/L)
Pb
melting range (°C)
c
c
c
c
c
1
2
3
4
5
6
dppe
4e
4a
-
-
0
1
2
3
1
0
0
49.0
59.1
63.4
53.5
75
162
193
67
11
15
188
236
96
20
2
29
58
14
73
85
7
2
<0.04
<0.08
-
-
2
-
-
1
-
134-138
186-189
136-138
oil
oil
155-159
-
0.0d
0.4e
C6F13
C6F13
C6F13
C8F17
4b
7
>300f
>300f
1
>90f
12
4c
<0.2
<0.2
>64f
>50g
i
4d h
6
0.4
-
a
Expressed as the amount of phosphine which can be dissolved in 1 L of pure solvent at 25 °C. Determined by gravimetric methods.
b
(PFMCH ) perfluoromethylcyclohexane) In a 1:1 (v/ v) mixture of PFMCH and toluene at 0 °C (P ) cfluorous phase/corganic phase). Determined
by gravimetric methods. The estimated error is (1 in the last digit. Not determined. No residue was found in the fluorous layer.e
c
d
f
g
Clear phase separation was achieved only after 15 h. Both 4b and 4c are completely miscible with PFMCH. No residue was found in
h
i
the toluene layer. Solubility in CF3C6H5 ) 14 g/L (5.8 mmol/L). Could not be determined due to low solubility in both toluene and
PFMCH.
THF and toluene increases upon trimethylsilyl function-
alization (entries 1 and 2). Furthermore, the fluorous
phase solubility of the diphosphines increases (entries
3-5, Rf ) C6F13) while the solubility in THF and toluene
decreases (entries 4 and 5) upon attachment of more
fluorotails to the phosphine. Compound 4a has only low
solubility in PFMCH, and compounds 4b and 4c dissolve
well in this fluorous solvent even allowing their purifica-
tion by fluorous phase extraction (see Experimental
Section). Whereas compound 4a is still highly soluble
in THF, 4b is only moderately soluble and 4c has low
solubility in THF. Compared to the fluorous triphen-
ylphosphine derivatives PAr3 (Ar ) C6H4-4-[SiMe3-n(CH2-
CH2C6F13)n]; n ) 0-3),9c the solubility of 4b and 4c in
PFMCH (>300 g/L) is in the same range (n ) 2: 615 g/L,
n ) 3: 502 g/L).
An important parameter for catalyst recycling by
fluorous biphasic extraction is the partition coefficient P
(P ) cfluorous phase/corganic phase) of a particular catalytic
complex and its fluorous ligands in fluorous biphasic
systems. The partition coefficients of 4a -c and 4e were
determined in a toluene/PFMCH biphasic system and
reflect the same trend as their solubility data, i.e.,
attachment of more perfluoroalkyl tails to the diphos-
phine leads to an improved affinity for the fluorous phase,
resulting in a maximum value for 4c (P > 50 with n )
3). In this way, diphosphines differ from the monophos-
phines PAr3 (Ar ) C6H4-4-[SiMe3-n(CH2CH2C6F13)n]; n )
0-3), where an optimum for n ) 2 was found.9c This
interesting phenomenon will be investigated further in
future publications.
the fluorous dppe derivatives containing 8 (59.1 wt % F)
or 12 perfluoroalkyl tails (63.4 wt % F) (compounds 4b
and 4c, respectively) are the preferred ligands for fluo-
rous phase metal-catalyzed organic synthetic applica-
tions. This aspect is currently under investigation.
Exp er im en ta l Section
Gen er a l. All experiments were performed in a dry dinitrogen
atmosphere using standard Schlenk techniques. Solvents were
stored over sodium benzophenone ketyl and distilled before use.
Fluorinated solvents (c-CF3C6F11 (Lancaster), FC-72 and CF3C6H5
(Acros)) were degassed and stored under dinitrogen atmosphere.
Fluorous alkylsilyl halides were prepared according to previously
reported procedures.9,11 Other chemicals were obtained from
commercial suppliers (Acros, Aldrich, Lancaster) and used as
delivered. Microanalyses were carried out by H. Kolbe, Mi-
kroanalytisches Laboratorium, Mu¨hlheim an der Ruhr. 19F NMR
spectra were externally referenced against C6F6 (δ ) -163
relative to CFCl3). The computer program gNMR, version 3.6,
Cherwell Scientific Publishing Limited, Oxford, was used for
simulation of 13C NMR spectra.
1,2-Bis[bis(4-br om op h en yl)p h osp h in o]eth a n e (3). p-Di-
bromobenzene (22.5 g, 95.3 mmol) was dissolved in a mixture
of n-hexane (300 mL) and diethyl ether (100 mL). To this solution
a solution of n-BuLi (1.64 M in pentane, 58.1 mL, 95.3 mmol)
was added. After stirring for 5 min, the mixture was cooled to
-78 °C followed by stirring for another 20 min. To the white
suspension was added 1,2-bis(dichlorophosphino)ethane (5.53 g,
23.8 mmol). The reaction mixture was allowed to reach room
temperature after 2 h. After stirring the reaction mixture for
another 15 h at room temperature, a degassed, saturated
aqueous NH4Cl-solution was added, and the two layers were
separated. The aqueous layer was washed with CH2Cl2 twice,
and the combined organic layers were dried on MgSO4. Volatiles
were evaporated in vacuo to afford 3 (14.46 g, 85%) as a slightly
yellow solid. Mp 176-179 °C. 1H NMR (200 MHz, CDCl3): δ
1.98 (ps t, J ) 3.8 Hz, 4H), 7.12-7.43 (m, 16 H); 13C NMR (50.3
MHz, CDCl3): δ 24.0 (d, 1J PC + 2J PC ) 2 Hz), 123.9 (s), 132.0 (t,
Con clu sion s
Highly fluorous dppe derivatives containing the (CH2-
CH2)nSiMe3-n spacer are readily accessible. The flexible
synthetic protocol developed, using the Si atom as a
branching point, makes this approach particularly useful
for parallel synthesis procedures. 31P NMR data suggest
that the electron density on the phosphorus atom is very
similar to the parent compounds dppe and 1,2-bis[bis{4-
(trimethylsilyl)phenyl}phosphino]ethane. Therefore, simi-
lar coordination chemistry with transition metals is to
be expected.
The preferential fluorous phase solubility of the novel
fluorous diphosphines increased with the number of tails
connected to the silicon atom, resulting in a highest
partition coefficient (P > 50, in favor of the fluorous
phase) for 4c. Hence, depending on the organic solvent
used and the number of fluorous extractions employed,
3J PC ) 7 Hz), 134.4 (t, 2J PC ) 19 Hz), 136.8 (t, 1J PC ) 14 Hz); 31
P
NMR (81.0 MHz, CDCl3): δ -13.8. Anal. Calcd for C26H20
-
Br4P2: C 43.74, H 2.82, P 8.68. Found: C 43.82, H 3.01, P 8.56.
Gen er a l P r oced u r e for p-Silyl-Su bstitu ted Dp p e De-
r iva t ives 4a -e. 1,2-Bis[bis(4-bromophenyl)phosphino]ethane
was dissolved in THF and cooled to -90 °C in an ethanol/liquid
nitrogen bath. To this solution was added 8 equiv of a solution
of t-BuLi in pentane. The reaction mixture was stirred for 30
min, while the temperature was kept below -60 °C. The green
suspension was treated with 4 equiv of alkylsilyl halide, and
the resulting solution was stirred below -60 °C for 1 h. The
slightly yellow solution thus formed was warmed to room
temperature in 6 h.
4a a n d 4e. After evaporating all solvents in vacuo, the white
solid was dissolved in degassed water/CH2Cl2. The organic layer
was separated, dried on MgSO4 and evaporated to dryness. The
products were isolated as white solids.

Notes
4b a n d 4c: The residue obtained after evaporating the
solvent in vacuo was dissolved in a two-phase system consisting
of methanol and FC-72. The fluorous layer was separated and
evaporated to dryness, giving a clear yellow oil. The compound
was further purified by Kugelrohr (120 °C, 0.1 mbar; 4b) or
washing with pentane (4c).
J . Org. Chem., Vol. 65, No. 17, 2000 5427
(20 mL), t-BuLi (8.6 mL 1.5 M; 12.9 mmol), and C8F17CH2CH2-
SiMe2Cl (3.49 g; 6.45 mmol) yielded 2.88 g (74%) of a brownish-
white solid: 1H NMR (200 MHz, C6D6/C6F6 1:1 (v:v)): δ 0.23 (s,
24H), 0.94 (m, 8H), 2.03-2.12 (m, 12H), 7.23-7.30 (m, 16H);
19F NMR (282 MHz, C6D6/C6F6 1:1 (v:v)): δ -127.6 (m, 2F),
-124.4 (m, 2F), -124.0 (m, 2F), -123.2 (m, 6F), -117.4 (m, 2F),
4d : The brownish-white solid, obtained after evaporation of
all THF, was washed with degassed water. The suspension was
filtered, washed with acetone, and dried in vacuo.
-82.8 (m, 3F); 31P NMR (81.0 MHz, C6D6/C6F6 1:1 (v:v)):
δ
-11.3. Anal. Calcd for C74H60F68P2Si4: C 36.80, H 2.50, P 2.56.
Found: C 36.65, H 2.59, P 2.48.
1,2-Bis[b is{4-((2-(p er flu or oh exyl)et h yl)d im et h ylsilyl)-
p h en yl}p h osp h in o]eth a n e (4a ). 3 (0.87 g; 1.22 mmol) in THF
(20 mL), t-BuLi (6.5 mL 1.5 M; 9.8 mmol), and C6F13CH2CH2-
SiMe2Cl (2.26 g; 5.12 mmol) yielded 2.08 g (85%) of a white
solid: 1H NMR (200 MHz, C6D6/C6F6 1:1 (v:v)): δ 0.25 (s, 24H),
0.96 (m, 8H), 2.01-2.12 (m, 12H), 7.22-7.29 (m, 16H); 13C NMR
1,2-B i s [b i s {4-(t r i m e t h y ls i ly l)p h e n y l}p h o s p h i n o ]-
eth a n e (4e). 3 (1.26 g; 1.76 mmol) in THF (30 mL), 9.4 mL of
a 1.5 M (14.1 mmol) t-BuLi solution, and Me3SiCl (0.80 g; 7.06
mmol) yielded 1.10 g (91%) of a white solid: 1H NMR (200 MHz,
CDCl3): δ 0.25 (s, 36H), 2.13 (ps t, J ) 4.4 Hz, 4H), 7.30-7.55
(m, 16H); 13C NMR (75.5 MHz, toluene-d8): δ -1.5 (s), 24.6 (s,
1J PC + 2J PC < 1 Hz), 132.3 (t, 2J PC ) 18.3 Hz), 133.3 (s), 139.8 (t,
1J PC ) 15.2 Hz), 140.3 (s); 31P NMR (81.0 MHz, C6D6/C6F6 1:1
(v:v)): δ -11.4. Anal. Calcd for C38H56P2Si4: C 66.42, H 8.21, P
9.01. Found: C 66.51, H 8.28, P 9.06.
Solu bility Stu d ies of 4a -e a n d d p p e. Saturated solutions
were prepared by stirring the fluorous diphosphine in the
appropriate solvent for 30 min at 25 °C. A sample (2.000 ( 0.002
mL) was taken after allowing the mixture to settle, and the mass
of this sample was determined. All solvent was removed in
vacuo, and the residue was kept under vacuum (0.1 mbar) for
15 h upon which the weight was constant within ( 1 mg, and
the weight of the residue was determined.
Deter m in ation of P ar tition Coefficien ts. A known amount
of diphosphine (between 12 and 84 µmol) was dissolved in a
biphasic system containing PFMCH (2.000 ( 0.002 mL) and
toluene (2.000 ( 0.002 mL). The mixture was stirred until all
of the compound had dissolved and then equilibrated in at 0 °C.
When two clear layers were obtained, an aliquot (500 ( 2 µL)
was removed from each layer by syringe. This was evaporated
to dryness, and the residue was kept under vacuum (0.1 mbar)
for 15 h upon which the weight was constant within (1 mg.
Subsequently, the weight of the residue was determined.
(75.5 MHz, toluene-d8): δ -4.1 (s), 5.0 (s), 24.2 (s, 1J PC + 2J PC
<
2
2
1 Hz), 26.0 (t, J FC ) 23.8 Hz), 132.5 (t, J PC ) 18.3 Hz), 133.6
(m), 137.8 (s), 140.2 (t, J PC ) 15.8 Hz); 19F NMR (282 MHz,
1
C6D6/C6F6 1:1 (v:v)): δ -128.2 (m, 2F), -125.1 (m, 2F), -124.9
(m, 2F), -124.0 (m, 2F), -117.9 (m, 2F), -82.8 (m, 3F); 31P NMR
(81.0 MHz, C6D6/C6F6 1:1 (v:v)): δ -11.3. Anal. Calcd for
C
66H60F52P2Si4: C 39.33, H 3.00, P 3.07. Found: C 39.40, H 3.09,
P 2.88.
1,2-Bis[b is{4-(d i(2-(p er flu or oh exyl)et h yl)m et h ylsilyl)-
p h en yl}p h osp h in o]eth a n e (4b). 3 (1.20 g; 1.68 mmol) in THF
(30 mL), t-BuLi (9.0 mL 1.5 M; 13.5 mmol), and (C6F13CH2CH2)2-
SiMeBr (6.7 g; 6.72 mmol), containing approximately 20 mol %
of (C6F13CH2CH2)2 (determined by 1H NMR) yielded 4.91 g (87%)
of a colorless oil: 1H NMR (200 MHz, C6D6/C6F6 1:1 (v:v)): δ
0.18 (s, 12H), 0.96 (m, 16H), 2.01 (m, 20H), 7.25 (m, 16H); 31P
NMR (81.0 MHz, C6D6/C6F6 1:1 (v:v)): δ -11.4. Anal. Calcd for
C
94H64F104P2Si4: C 33.77, H 1.93, P 1.85. Found: C 33.71, H
1.83, P 1.82.
1,2-Bis[bis{4-(tr i(2-(p er flu or oh exyl)eth yl)silyl)p h en yl}-
p h osp h in o]eth a n e (4c). 3 (0.47 g; 0.66 mmol) in THF (15 mL),
t-BuLi (3.5 mL 1.5 M; 5.3 mmol), and (C6F13CH2CH2)3SiBr (3.58
g; 2.64 mmol), containing approximately 30 mol % of (C6F13CH2-
1
CH2)2 (determined by H NMR) yielded 1.60 g (55%) of a yellow
oil: 1H NMR (200 MHz, C6D6/C6F6 1:1 (v:v)): δ 1.01 (m, 24H),
1.95 (m, 28H), 7.23 (m, 16H); 31P NMR (81.0 MHz, C6D6/C6F6
1:1 (v:v)): δ -11.4. Anal. Calcd for C122H68F156P2Si4: C 31.37,
H 1.47, P 1.33. Found: C 31.46, H 1.38, P 1.44.
Ack n ow led gm en t. We thank Elf Atochem Vlissin-
gen B.V. and the Dutch Ministry for Economic Affairs
(SENTER/BTS) for financial support.
1,2-Bis[b is{4-((2-(p er flu or ooct yl)et h yl)d im et h ylsilyl)-
p h en yl}p h osp h in o]eth a n e (4d ). 3 (1.15 g; 1.61 mmol) in THF
J O000312K