Increasing the lipophilic character of tetraphenylborate anions through silyl substituents

Article abstract of DOI:10.1021/om0009177

Trimethylsilyl- and dimethyl(1H,1H,2H,2H-perfluorooctyl)silyl substituents have been introduced in the para position of tetraphenylborate anions, resulting in enhanced solubility of their complexes n-Bu₄N[B(C₆H₄-SiMe₂

Full text of DOI:10.1021/om0009177

2114
Organometallics 2001, 20, 2114-2117
Notes
In cr ea sin g th e Lip op h ilic Ch a r a cter of
Tetr a p h en ylbor a te An ion s th r ou gh Silyl Su bstitu en ts
J oep van den Broeke,† Martin Lutz,‡ Huub Kooijman,‡ Anthony L. Spek,‡,
Berth-J an Deelman,*,§ and Gerard van Koten†
Department of Metal-Mediated Synthesis, Debye Institute, Utrecht University, Padualaan 8,
3584 CH Utrecht, The Netherlands, Department of Crystal and Structural Chemistry,
Bijvoet Center for Biomolecular Research, Utrecht University, Padualaan 8,
3584 CH Utrecht, The Netherlands, and ATOFINA Vlissingen B.V., P.O. Box 70,
4380 AB Vlissingen, The Netherlands
Received October 30, 2000
Summary: Trimethylsilyl- and dimethyl(1H,1H,2H,2H-
perfluorooctyl)silyl substituents have been introduced in
the para position of tetraphenylborate anions, resulting
in enhanced solubility of their complexes n-Bu4N[B(C6H4-
SiMe2R-4)4] (R ) Me, CH2CH2C6F13) and [Rh(dppe)2]-
[B(C6H4SiMe2R-4)4] (dppe ) 1,2-bis(diphenylphosphino)-
ethane, R ) Me, CH2CH2C6F13) in apolar organic
solvents.
such as super critical carbon dioxide.5a,b Herein we
report the preparation of large and weakly coordinating
trimethylsilyl- and perfluoroalkylsilyl-substituted tet-
raphenylborate anions, which are more lipophilic than
[BPh4]-, but in a chemical sense very similar to this
anion.
Resu lts a n d Discu ssion
In tr od u ction
Starting from p-bromo(trimethylsilyl)benzene and
p-bromo[dimethyl(1H,1H,2H,2H-perfluorooctyl)silyl]ben-
zene, 1a and 1b were prepared. Ion exchange with
n-Bu4NF and [Rh(dppe)2]Cl yielded the corresponding
complexes 3 and 4 (Scheme 1). To assess the influence
of the silyl substitution on the tetraphenylborate, single
crystals of 2a and 4a were obtained. Their molecular
structures in the solid state were determined by single-
crystal X-ray diffraction (Figures 1 and 2, respectively).6
Weakly coordinating anions are of interest for a range
of applications that require generation and stabilization
of highly reactive cationic species.1,2 A lot of research
has been directed at reducing the nucleophilicity of such
anions by increasing their steric requirements, as in
[B(C6F4SiR3)4]- 3 and [MeB(2-C6F4C6F5)3]-,4 or by using
polyhedral carboranes such as [CB11H12]-, [CB11H6Cl6]-,
and [CB11HF11]-.1a,b However, relatively simple tet-
raphenylborates such as [B{3,5-C6H3(CF3)2}4]- (TFPB)
and [B(C6F5)4]- remain the most widely used,1a because
of their easy synthesis. Another interesting implication
of the use of TFPB and [B(C6F4SiR3)4]- is their lipophilic
behavior.3,5 Especially TFPB is known for increasing the
solubility of transition metal complexes in apolar media
† Debye Institute.
‡ Bijvoet Center.
To whom correspondence concerning crystallographic data should
be addressed.
§ ATOFINA, currently based at the Debye Institute. Fax: +31
302523615. E-mail: b.j.deelman@chem.uu.nl.
(1) Recent reviews: (a) Lupinetti, A. J .; Strauss, S. H. Chemtracts
1998, 11, 565. (b) Reed, C. A. Acc. Chem. Res. 1998, 32, 1025. (c)
Strauss, S. H. Chem. Rev. 1993, 93, 927.
(2) Selected references: (a) Lancaster, S. J .; Walker, D. A.; Thornton-
Pett, M.; Bochmann, M. Chem. Commun. 1999, 1533. (b) Xie, Z.;
Manning, J .; Reed, R. W.; Mathur, R.; Boyd, P. D. W.; Benesi, A.; Reed,
C. A. J . Am. Chem. Soc. 1996, 118, 2922. (c) Giardello, M. A.; Eisen,
M. S.; Stern, S. L.; Marks, T. J . J . Am. Chem. Soc. 1993, 115, 3326.
(d) Brookhart, M.; Grant, B.; Volpe, A. F. Organometallics 1992, 11,
3920.
(3) J ia, L.; Yang, X.; Stern, C. L.; Marks, T. J . Organometallics 1997,
16, 842.
(4) Chen, Y.-X.; Stern, C. L.; Marks, T. J . J . Am. Chem. Soc. 1997,
119, 2582.
F igu r e 1. Molecular structure of 2a with ellipsoids at 30%
probability level. H atoms were omitted. Selected bond
lengths (Å) and angles (deg): B-C(1) ) 1.658(4), B-C(10)
) 1.643(5), B-C(19) ) 1.647(4), B-C(28) ) 1.655(4), Na-
O(1) ) 2.685(3), Na-O(2) ) 2.712(3), Na-O(3) ) 2.712(3),
Na-O(4) ) 2.704(4), Na-O(5) ) 2.822(3), Na-O(6) )
2.786(3), Na-O(7) )2.268(5), Na-O(8) ) 2.284(4), C(1)-
B-C(10) ) 106.6(3), C(1)-B-C(19) ) 111.9(2), C(1)-B-
C(28) ) 108.8(2), C(10)-B-(C19) ) 110.9(2), C(10)-B-
C(28) ) 111.1(2), C(19)-B-C(28) ) 107.6 (3).
(5) (a) Kainz, S.; Brinkmann, A.; Leitner, W.; Pfaltz, A. J . Am. Chem.
Soc. 1999, 121, 6421. (b) Burk, M. J .; Feng, S.; Gross, M. F.; Tumas,
W. J . Am. Chem. Soc. 1995, 117, 8277. (c) Iwamoto, H.; Sonoda, T.;
Kobayashi, H. Tetrahedron Lett. 1983, 24, 4703.
10.1021/om0009177 CCC: $20.00 © 2001 American Chemical Society
Publication on Web 04/19/2001

Notes
Organometallics, Vol. 20, No. 10, 2001 2115
Sch em e 1. Syn th esis of th e Va r iou s p-Silyl-Su bstitu ted Tetr a a r yl Bor a te Com p lexes
The structural similarity of the borate anions in 2a and
4a with those in [Na(18-crown-6)(H2O)2][BPh4],7a
[Na(benzo-15-crown-5)2][BPh4],7b and [Rh(HOCH(CH2-
PPh2)2)2][BPh4]8 indicates that the influence of the silyl
substitution on the geometry of the borate anion is not
significant, and its weakly coordinating character is at
least comparable to [BPh4]-. This is further supported
by 11B NMR spectroscopy in solution; the chemical shifts
measured in methanol-d4 for all compounds described
herein hardly deviate from that measured for sodium
tetraphenylborate.9
A difference between fluorous borate 1b and nonfluo-
rous 1a was observed in the IR spectra of these
compounds. The spectrum of 1a shows the presence of
coordinated water resulting from the aqueous workup,
whereas 1b is isolated as a solvent-free salt. The
absence of coordinated H2O in 1b is confirmed by
elemental analysis and is remarkable, as sodium bo-
rates are usually obtained free of solvent only after
thorough drying.10 The lack of solvent coordination in
1b could be caused by the presence of stabilizing
Na‚‚‚F-C interactions11,12 between the Na+ cation and
the perfluoroalkyl tail, thereby eliminating the need for
polar solvent (i.e., H2O) coordination. IR data were
inconclusive in this respect, as no changes in the C-F
stretching region (1200-1350 cm-1) of the IR spectrum
of 1b relative to that of 3b were observed.11a,13 Attempts
to detect these interactions either by 19F NMR spec-
troscopy in solution or by determination of a molecular
structure in the solid state were hampered by the low
solubility of 1b in apolar solvents as well as the
impossibility to obtain 1b in single crystalline form.
The solubility of 1, 3, and 4 in various solvents was
explored, which revealed that the introduction of per-
(6) Crystal data for 2a : C56H92BNaO8Si4, monoclinic, spacegroup
P21/c (no. 14), with a ) 13.540(2), b ) 20.606(3), c ) 27.693(3) Å, â )
118.86(2)°, V ) 6767.1(16) Å3, Z ) 4, Dcalcd ) 1.020 g cm-3. All data,
where relevant, are given without disordered solvent contribution;
44 964 reflections measured (Nonius KappaCCD diffractometer, 150
K, Mo KR radiation), 12 222 unique. The structure was solved by
automated direct methods (SHELXS86) and refined on F2 (SHELXL-
97-2, 631 parameters). A disordered solvent area (792 Å, 187 e,
probably THF) was incorporated in the model using PLATON/
SQUEEZE. Several of the SiMe3 groups and one of the phenyl rings
of the anion display conformational disorder. The available data did
not allow for the refinement of a disorder model. wR2 ) 0.2304, R1 )
0.0793 for 9530 I > 2σ(I), S ) 1.069, -0.48 < ∆F < 0.96 e Å-3. Crystal
data for 4a : C88H100BP4RhSi4, monoclinic, spacegroup P21 (no. 4), with
a ) 14.7259(2), b ) 20.1809(2), c ) 16.4196(2) Å, â ) 96.5775(4)°, V )
4847.49(10) Å3, Z ) 2, Dcalcd ) 1.033 g cm-3. All data, where relevant,
are given without disordered solvent contribution; 96 384 reflections
measured (as for 2a ), 22 082 unique. The structure was solved by
automated direct methods (SHELXS97) and refined on F2 (SHELXL-
97-2, 992 parameters). A disordered solvent area (1001 Å, 376 e) was
incorporated in the model using PLATON/SQUEEZE. A two-site
disorder model was introduced to describe the rotational disorder of
the phenyl moieties around C3-P3; the occupancy of the major
component refined to 0.537(9). wR2 ) 0.0880, R1 ) 0.0348 for 19688I
> 2σ(I), S ) 1.039, -0.36 < ∆F < 0.39 e Å-3
.
(7) (a) Seik Weng Ng. Z. Kristallogr.-New Cryst. Struct. 1998, 213,
159. (b) Owen, J . D. J . Chem. Soc., Dalton Trans. 1980, 1066.
(8) Scherer, J .; Huttner, G.; Buchner, M.; Bakos, J . J . Organomet.
Chem. 1996, 520, 45.
(9) The 11B NMR spectrum of NaBPh4 in CD3OD shows a resonance
at δ -2.76, which is similar to the chemical shifts of the 11B resonances
found for 1b (δ -2.77), 2a (δ -2.60), 3a (δ -2.79), 3b (δ -2.79), 4a (δ
-2.80), and 4b (δ -2.80).
(10) (a) Wittig, G.; Raff, P. Liebigs Ann. Chem. 1950, 573, 195. (b)
Nishida, H.; Takada, N.; Yoshimura, M.; Sonoda, T.; Kobayashi, H.
Bull. Chem. Soc. J pn. 1984, 57, 2600. (c) Bahr, S. R.; Boudjouk, P. J .
Org. Chem. 1992, 57, 5545.
F igu r e 2. Molecular structure of 4a with ellipsoids at 30%
probability level. H atoms were omitted. Selected bond
lengths (Å) and angles (deg): B-C(53) ) 1.637(3), B-C(62)
) 1.637(3), B-C(71) ) 1.662(3), B-C(80) ) 1.653(3), Rh-
P(1) ) 2.2979(6), Rh-P(2) ) 2.2997(6), Rh-P(3) ) 2.2833-
(6), Rh-P(4) ) 2.2956(6), Rh-C(57) ) 6.260(2), C(53)-B-
C(62) ) 109.03(16), C(53)-B-C(71) ) 108.89(17), C(53)-
B-C(80) ) 108.02(16), C(62)-B-C(71) ) 108.75(16), C(62)-
B-C(80) ) 110.75(17), C(71)-B-C(80) ) 111.35(16), P(1)-
Rh-P(2) ) 83.74(2), P(1)-Rh-P(3) ) 163.09(2), P(1)-Rh-
P(4) ) 98.68(2), P(2)-Rh-P(3) ) 99.07(2), P(3)-Rh-P(4)
) 83.54(2).
(11) (a) For a Na...F-C interaction, see: Samuels, J . A.; Lobkovsky,
E. B.; Streib, W. E.; Folting, K.; Huffman, J . C.; Zwanziger, J . W.;
Caulton, K. G. J . Am. Chem. Soc. 1993, 115, 5093. (b) For a Zr‚‚‚F-C
interaction, see: Karl, J .; Erker, G.; Fro¨hlich, R. J . Am. Chem. Soc.
1997, 119, 11165.
(12) Another possible interaction of Na with the borate anion would
be η6-coordination with a phenyl group. This is a well-known coordina-
tion mode of [BPh4]- toward metal ions (ref 1c and Aresta, M.;
Quaranta, E.; Tommasi, I. New J . Chem. 1997, 21, 595.). However,
the ease with which 1b, compared to 1a , is obtained free of water
suggests involvement of the perfluoroalkyl groups.

2116 Organometallics, Vol. 20, No. 10, 2001
Notes
Ta ble 1. Solu bility of th e Bor a te Com p lexes in
Hexa n esa
in the anion. These lipophilic tetraphenylborate anions
with a more complex structure can be obtained through
a facile synthetic procedure by using the silyl center as
a connecting point.18 A further increase of the fluorous
content of these borates is needed to achieve the desired
solubility in apolar and fluorous (e.g., FC-72) solvents.
Most importantly, it was shown that the introduction
of these fluorous silyl substituents leaves the structural
properties and the coordination behavior of these anions
almost unaffected, thus rendering them alternatives for
the TFPB anion and of interest for application in
biphasic catalysis using apolar media or for catalysis
in supercritical CO2.
compound
µmol/Lb
<11
<8
mg/Lb
<7
<7
[n-Bu4N][BPh4]c
3a c
3bd
4.0 × 103
8.7 × 103
[Rh(dppe)2][BPh4]c
<0.4
0.4
5.8
<0.7
0.7
17
4a
4b
a
A mixture of hexane isomers, predominantly n-hexane and
b
methylcyclopentane, was used. Expressed as the amount of
borate complex that can be dissolved in 1 L of pure solvent at 25
°C. Determined by ICP/AAS analysis for [B] and [Rh]. c Below the
d
detection limit for ICP-AAS. Solubility determined using gravi-
metric methods.
Exp er im en ta l Section
fluoroalkylsilyl groups in BPh4- has a marked effect on
the solubility of the borate complexes. Introduction of
both trimethylsilyl and perfluoroalkylsilyl groups re-
sults in poor solubility in water for sodium salts 1a and
1b (<0.14 mmol/L), whereas NaBPh4 shows excellent
solubility (>0.30 mol/L) in this solvent.14 However,
solubility of 1a and 1b in a noncoordinating solvent,
such as hexanes, remains low too (<0.14 mmol/L).
Exchange of sodium for a tetrabutylammonium cation
results in increased solubility of fluorous compound 3b
in hexanes, whereas nonfluorous 3a remains essentially
insoluble (Table 1). The influence of the fluorous tail
on the solubility of the rhodium complex is less dra-
matic, but does result in an increased solubility in
hexanes for 4b (6 µmol/L) when compared to 4a (0.4
Gen er a l P r oced u r es. All reactions were performed under
dry N2 atmosphere using standard Schlenk techniques. Tet-
rahydrofuran (THF), diethyl ether (Et2O), hexane, and pentane
were distilled from sodium benzophenone ketyl. p-Bromo-
(trimethylsilyl)benzene19 and p-bromo(dimethyl(1H,1H,2H,2H-
perfluorooctyl)silyl)benzene17b,c were synthesized according to
literature procedures. All other chemicals were used as
received. NMR spectra were recorded on Varian Mercury 200
(1H and 31P) and Varian Inova 300 (1H, 11B, 13C, and 19F)
spectrometers with TMS (1H, 13C), CFCl3 (19F), BF3‚Et2O (11B),
and H3PO4 (85%) (31P) as external references. Elemental
analyses and ICP/AAS analyses were carried out by H. Kolbe,
Mikroanalytisches Laboratorium, Mu¨hlheim an der Ruhr.
Infrared spectra were recorded on a Mattson Galaxy FT-IR
5000 spectrometer.
15
Sodium Tetrakis[p-(trimethylsilyl)phenyl]borate Hexahy-
d r a t e (1a ) a n d 18-Cr ow n -6-bis(t et r a h yd r ofu r a n )-So-
d iu m Tetr a k is[p-(tr im eth ylsilyl)p h en yl]bor a te (2a ). To
a solution of p-bromo(trimethylsilyl)benzene (9.00 g, 39.1
mmol) in Et2O (100 mL) was slowly added t-BuLi (52 mL, 1.5
M in pentane, 79.2 mmol) at -78 °C. The resulting solution
was stirred for 3 h and allowed to warm to 0 °C. After cooling
to -78 °C, BF3‚Et2O (0.82 mL, 6.53 mmol) was added, and
the solution was allowed to reach room temperature over a
period of 16 h. The resulting clear yellow solution was slowly
poured into a saturated aqueous NaCl solution (100 mL) and
the Et2O layer separated. After extraction of the aqueous layer
with Et2O (3 × 50 mL), the combined organic layers were
washed with H2O (50 mL) and dried over MgSO4. Removal of
the solvent and washing with pentane yielded 3.75 g (82%
yield, based on boron) of a white solid. 1H NMR (methanol-d4,
µmol/L) and reference compound [Rh(dppe)2]BPh4
(<0.4 µmol/L). The increased solubility of 4b was also
visible to the naked eye, as only 4b gave a distinctly
yellow-colored hexane layer. Although the hexane solu-
tions of 3b and 4b appear to be real solutions to the
naked eye, the presence of colloidal aggregates or
micelles cannot be excluded a priori and will be the
subject of further research.
The solubility of perfluoroalkyl-substituted borates 3b
and 4b in the fluorocarbon solvent FC-7216 was also
explored. This was found to be low for both compounds
(3b, 52 µmol/L; 4b, no color change observed in FC-72,
implicating solubility well below 6 µmol/L). This can be
explained by the combination of a relatively low fluorine
content of these compounds, 45 and 35 wt %, respec-
tively, and their ionic nature. It has been reported that
the fluorine content of neutral phosphines and metal-
phosphine complexes should be ca. 60% or higher to
achieve high or preferential solubility in fluorous sol-
vents.17
3
300.1 MHz): δ 7.36 (m, 8H, Aro), 7.17 (d, J HH ) 6.0 Hz, 8H,
Arm), 4.85 (s, 12H, H2O), 0.22 (s, 36H, SiCH3). 13C{1H} NMR
1
(methanol-d4, 75.5 MHz): δ 167.3 (q, J BC ) 49.3 Hz, C-B),
137.7 (Aro), 132.9 (C-Si), 132.3 (Arm), 0.27 (SiCH3). 11B{1H}
1
NMR (methanol-d4, 96.3 MHz): δ -2.55 (t, J BC ) 24.4 Hz).
IR (KBr, cm-1): 3485 (s), 3045 (m), 2955 (s), 1635 (w), 1577
(m), 1259 (s), 1143 (s), 1087 (m), 841 (s), 804 (m).
In conclusion, the present results show that the
solubility of ionic tetraphenylborate complexes, espe-
cially tetrabutylammonium tetraphenylborate, in al-
kane solvents can be improved by the introduction of
dimethyl(1H,1H,2H,2H-perfluorooctyl)silyl substituents
Light yellow crystals of borate 2a were grown by slow
diffusion of hexane into a solution of 1a (0.40 g, 0.57 mmol)
and THF (15 mL) in the presence of 18-crown-6 (0.29 g, 1.10
mmol). 1H NMR (methanol-d4, 300.1 MHz): δ 7.36 (m, 8H,
Aro), 7.19 (d, 3J HH ) 6.0 Hz, 8H, Arm), 3.72 (m, 8H, THF), 3.59
(s, 24H, 18-crown-6), 1.86 (m, 8H, THF), 0.21 (s, 36H, SiCH3).
13C{1H} NMR (methanol-d4, 75.5 MHz): δ 167.3 (q, 1J BC ) 49.3
Hz, C-B), 137.7 (Aro), 132.8 (C-Si), 132.4 (Arm), 71.9 (18-
crown-6), 67.7 (R-THF), 27.4 (â-THF), 0.36 (SiCH3). 11B{1H}
(13) (a) Adams, D. M. Metal-Ligand and Related Vibrations;
Edward Arnold (Publishers) Ltd: London, 1967. (b) Douay, M. C.;
Bopegedera, A. M. R. P.; Brazier, C. R.; Bernath, P. F. Chem. Phys.
Lett. 1998, 148, 1.
(14) Bueechl, H. In Advances in Analytical Chemistry and Instru-
mentation; Reilly, C. N., Ed.; Wiley: New York, 1960; Vol. 1, p 10.
(15) Faraone, F. J . Chem. Soc., Dalton Trans. 1975, 541.
(16) FC-72 is a mixture of perfluorohexanes.
(17) (a) Horva´th, I. T. Acc. Chem. Res. 1998, 31, 641. (b) Richter,
B.; Deelman, B.-J .; van Koten, G. J . Mol. Catal. (A) 1999, 145, 317. (c)
Richter, B.; de Wolf, E.; van Koten, G.; Deelman, B.-J . J . Org. Chem.
2000, 65, 3885.
1
NMR (methanol-d4, 96.3 MHz): δ -2.60 (t, J BC ) 24.4 Hz).
(18) (a) Richter, B.; Spek, A. L.; van Koten, G.; Deelman, B.-J . J .
Am. Chem. Soc. 2000, 122, 3945. (b) Richter, B.; Deelman, B.-J .; van
Koten, G. European Patent Appl. 98203308.6.
(19) Wu, R.; Schumm, J . S.; Pearson, D. L.; Tour, J . M. J . Org. Chem.
1996, 61, 6906.

Notes
Organometallics, Vol. 20, No. 10, 2001 2117
Anal. Calcd for C56H92BNaO8Si4: C, 64.71; H, 8.92; Si, 10.81.
Found: C, 64.71; H, 8.93; Si, 11.74.
Rh od iu m (I) [Bis(1,2-bis(d ip h en ylp h osp h in o)eth a n e)]
Tet r a k is[p-(t r im et h ylsilyl)p h en yl]b or a t e (4a ). 1,2-Bis-
(diphenylphosphino)ethane (0.46 g, 1.17 mmol) in CH2Cl2 (5
mL) was slowly added to a solution of [Rh(1,5-COD)Cl]2 (135.6
mg, 0.28 mmol) in CH2Cl2 (5 mL). After stirring for 1 h, 1a
(0.41 g, 0.57 mmol) suspended in 1-propanol (5 mL) was added
slowly. The resulting mixture was stirred for 4 h and filtered,
and volatiles were removed in vacuo. The solid was taken up
in acetone, the resulting solution was filtered, and upon
addition of hexane, 0.63 g (76%) of a light orange solid
precipitated. Crystals were grown by slow diffusion of Et2O
Sod iu m Tetr a k is[p-{d im eth yl(1H,1H,2H,2H-p er flu or o-
octyl)silyl}p h en yl]bor a te (1b). Preparation of compound 1b
was carried out using a procedure similar to that employed
for the preparation of 1a . Starting from p-bromo{dimethyl-
(1H,1H,2H,2H-perfluorooctyl)silyl}benzene (2.88 g, 5.12 mmol)
in a Et2O/hexane mixture (1:1, 50 mL), t-BuLi (6.8 mL, 1.5 M
in pentane, 10.2 mmol), and BF3‚Et2O (0.11 mL, 0.85 mmol)
1
yielded 1.60 g (97% yield, based on boron) of a white solid. H
NMR (methanol-d4, 300.1 MHz): δ 7.34 (m, 8H, Aro), 7.20 (d,
3J HH ) 7.8 Hz, 8H, Arm), 2.05 (m, 8H, CH2CF2), 0.86 (m, 8H,
SiCH2), 0.30 (s, 24H, SiCH3). 13C{1H} NMR (methanol-d4,
75.5): δ 168.7 (C-B), 137.7 (Aro), 132.5 (Arm), 129.7 (C-Si),
28.0 (CH2CF2), 7.3 (SiCH2), -2.3 (SiCH3). 11B{1H} NMR
(methanol-d4, 96.3 MHz): δ -2.77 (s). 19F NMR (methanol-d4,
282.5 MHz): δ -79.0 (m, 3F), -113.6 (m, 2F), -119.5 (m, 2F),
-120.5 (m, 2F), -121.0 (m, 2F), -123.9 (m, 2F). IR (KBr, cm-1):
3045 (w), 2980 (w), 1361 (w), 1317 (w), 1240 (s), 1213 (s),
1143 (m), 1069 (m), 898 (m), 841 (s), 798 (s), 530 (s). Anal.
Calcd for C64H56BF52NaSi4: C, 39.23; H, 2.88; B, 0.55; F, 50.42;
Na, 1.17. Found: C, 39.18; H, 3.02; B, 0.54; F, 50.27; Na, 1.25.
Tetr abu tylam m on iu m Tetr akis[p-(tr im eth ylsilyl)ph en -
yl]bor a te (3a ). n-Bu4NF (0.86 mL, 1 M in THF, 0.86 mmol)
was added to a solution of 1a (0.32 g, 0.43 mmol) in THF (25
mL). After stirring for 1.5 h, the solution was evaporated to
dryness. H2O (10 mL) was added, and the mixture was stirred
for 30 min. The solid was collected and washed with H2O (10
mL). The resulting solid was dried in vacuo, yielding 0.24 g
1
into a CHCl3 solution of 4a . H NMR (CDCl3, 300.1 MHz): δ
3
7.44 (m, 8H, Aro), 7.34 (m, 8H, J HH ) 6.0 Hz, Arm), 7.18 (m,
40H, P-Ph) 2.07 (m, 8H, P-(CH2)2-P), 0.14 (s, 36H, SiCH3).
1
13C{1H} NMR (CDCl3, 75.5 MHz): δ 165.5 (q, J BC ) 48.8 Hz,
B-C), 136.0(s), 134.6(s), 133.4(s), 131.5 (m, P-C), 131.3(s),
130.9(s), 128.8(s), 28.7 (m, P-(CH2)2-P), -0.3 (SiCH3). 11B-
{1H} NMR (methanol-d4, 96.3 MHz): δ -2.80 (s). 31P NMR
1
(CDCl3, 81.0 MHz): δ 58.3 (d, J RhP ) 132.5 Hz). Anal. Calcd
for C88H100BP4RhSi4: C, 70.10; H, 6.69; P, 8.22; Si, 7.45.
Found: C, 69.97; H, 6.82; P, 8.15; Si, 7.36.
Rh od iu m (I) [Bis(1,2-bis(d ip h en ylp h osp h in o)eth a n e)]
Tetr akis[p-{dim eth yl (1H,1H,2H,2H-per flu or ooctyl)silyl}-
p h en yl]bor a te (4b). To a solution of [Rh(COD)Cl]2 (51.8 mg,
0.12 mmol) in CH2Cl2 (5 mL) was slowly added dppe (0.18 g,
0.45 mmol) in CH2Cl2 (2 mL). After stirring for 1 h, 1b (0.24
g, 0.12 mmol) dissolved in methanol (2 mL) was added slowly.
The resulting mixture was stirred for 1.5 h and filtered, and
volatiles were removed in vacuo. The solid was then taken up
in CHCl3, the resulting solution was filtered, and upon addition
of diethyl ether, 0.46 g (68%) of a bright yellow solid precipi-
1
(65%) of a white solid. H NMR (methanol-d4, 300.1 MHz): δ
3
7.35 (m, 8H, Aro), 7.19 (d, 8H, J HH ) 7.5 Hz, Arm), 3.13 (m,
8H, NCH2), 1.58 (m, 8H, NCH2CH2), 1.37 (m, 8H, CH2CH2-
CH2), 1.02 (t, 12H, CH2CH3), 0.22 (s, 36H, SiCH3). 13C{1H}
NMR (methanol-d4, 75.5 MHz): δ 166.3 (q, C-B), 137.8 (Aro),
133.0 (C-Si), 132.4 (Arm), 60.4 (NCH2), 25.6 (NCH2CH2), 21.6
(CH2CH2CH3), 14.8 (CH2CH3), 0.3 (SiCH3). 11B{1H} NMR
1
tated. H NMR (CDCl3, 300.1 MHz): δ 7.44 (m, 8H, Aro), 7.34
1
(d, 8H, J HH ) 6.0 Hz, Arm), 7.18 (m, 40H, P-Ph), 2.12 (m,
8H, P-(CH2)2-P), 2.05 (m, 8H, CH2CF2), 0.90 (m, 8H, CH2-
Si), 0.14 (s, 24H, SiCH3). 13C{1H} NMR (CDCl3, 75.5 MHz): δ
1
165.5 (q, J BC ) 48.8 Hz, B-C), 136.0(s), 134.6(s), 133.4(s),
(methanol-d4, 96.3 MHz): δ -2.79 (s). Anal. Calcd for C52H88
-
132.3, 131.5 (m, P-C), 131.3(s), 130.9(s), 128.8(s), 28.7 (CH2-
BNSi4: C, 73.44; H, 10.43; N, 1.65. Found: C, 73.15; H, 10.51;
N, 1.68.
1
CF2), 26.3 (t, J PC ) 23.7 Hz, P-(CH2)2-P), 5.7 (SiCH2), -0.3
(SiCH3). 11B{1H} NMR (methanol-d4, 96.3 MHz): δ -2.80 (s).
Tet r a b u t yla m m on iu m Tet r a k is[p -{d im et h yl(1H ,1H ,
2H,2H-p er flu or ooctyl)silyl}p h en yl]bor a te (3b). Prepara-
tion of compound 3b was carried out using a procedure similar
to that employed for the preparation of 3a . Starting from 1b
(0.23 g, 0.12 mmol) and n-Bu4NF (0.24 mL, 1 M in THF, 0.24
mmol) yielded 0.12 g (46%) of an off-white waxy solid. 1H NMR
(methanol-d4, 200.1 MHz): δ 7.34 (m, 8H, Aro), 7.15 (d, 8H,
3J HH ) 7.4 Hz, Arm), 3.29 (m, 8H, NCH2), 2.01 (m, CH2CF2),
1.64 (m, 8H, NCH2CH2), 1.41 (m, 8H, CH2CH2CH2), 1.01 (t,
12H, CH2CH3), 0.86 (m, 8H, SiCH2) 0.19 (s, 36H, SiCH3). 13C-
{1H} NMR (methanol-d4, 75.5 MHz): δ 169.2 (q, C-B), 138.2
(Aro), 132.9 (C-Si), 130.3 (Arm), 60.6 (NCH2), 28.2 (t, CH2CF2),
25.8 (NCH2CH2), 12.7 (CH2CH2CH3), 14.9 (CH2CH3), 7.5
(SiCH2), -2.1 (SiCH3). 11B{1H} NMR (methanol-d4, 96.3
MHz): δ -2.79 (s). IR (KBr, cm-1): 3045 (w), 2962 (w), 1579
(w), 1479 (w), 1363 (m), 1248 (s), 1209 (s), 1143 (m), 1066 (m),
1022 (m), 896 (m), 839 (s), 794 (s), 530 (s). Anal. Calcd for
C80H92BF52NSi4: C, 44.10; H, 4.26; N, 0.64; F, 45.35. Found:
C, 43.83; H, 4.34; N, 0.56; F, 45.26.
1
31P NMR (CDCl3, 81.0 MHz): δ 58.3 (d, J RhP ) 132.5 Hz).
Anal. Calcd for C116H104BF52P4RhSi4: C, 49.13; H, 3.70; F,
34.84; P, 4.37; Si, 3.96. Found: C, 49.25; H, 3.66; F, 34.67; P,
4.85; Si, 4.05.
Ack n ow led gm en t. This work was financially sup-
ported by ATOFINA Vlissingen B.V., the Dutch Minis-
try of Economic Affairs (Senter/BTS), and (A.L.S., M.L.)
the Council for Chemical Sciences of The Netherlands
Organization for Scientific Research (CW-NWO).
Su p p or tin g In for m a tion Ava ila ble: Solubility studies,
crystal data, and structure refinement details for 2a and 4a .
This material is available free of charge via the Internet at
http://pubs.acs.org.
OM0009177